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Every NCERT book that matters for UPSC — open a book, then a chapter. Learn each chapter's concepts, then how UPSC tests them — with diagrams, flowcharts and the past questions to attempt.
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← Science — all chaptersMetals and Non-metals
Start here: why this chapter matters
In simple wordsYour steel spoon, copper wire, aluminium foil and gold ring are metals; the oxygen you breathe, the carbon in pencil lead and the sulphur in a matchstick are non-metals. This chapter explains why metals shine, bend and conduct, why some metals burst into flame in water while gold never tarnishes, how a mineral dug from the ground becomes a pure metal, and why iron rusts — and how we stop it.
This is the third chapter of NCERT's Class 10 Science textbook (pages 37–57 of the 2026-27 reprint; the contents page and the PDF agree). It has five parts — physical properties (3.1), chemical properties of metals with the reactivity series (3.2), how metals and non-metals react, i.e. ionic compounds (3.3), occurrence and extraction of metals (3.4) and corrosion with its prevention and alloys (3.5) — with 14 activities, Figures 3.1–3.13 plus an unnumbered exercise figure and a photograph of the Delhi iron pillar, Tables 3.1–3.4, two ‘Do You Know?’ boxes and one more at the end, a ‘More to Know!’ box, five in-text question boxes, a summary and 16 exercise questions. As in the previous two chapters, every equation on this page is checked in the source — atoms and electric charge, including the electron half-equations.
- Neighbouring chapters: Chemical Reactions and Equations (Class 10, Chapter 1) gave displacement reactions (Activity 1.9 — the iron nail in copper sulphate), oxidation and reduction, and corrosion; Acids, Bases and Salts (Chapter 2) gave ‘acid + metal → salt + hydrogen’ and ‘metal oxides are basic’. The next chapter, Carbon and its Compounds, sets covalent bonds against this chapter's ionic ones. Geography gives the setting: Minerals and Energy Resources (Class 10 — ores and where they are mined) and Manufacturing Industries (Class 10 — iron and steel, aluminium smelting).
- Prelims — science: UPSC has asked about galvanising (1982, 1983, 1992, 1994), stainless steel (1980), ‘which is not an alloy’ (1984, 1989), solder (2006), 18-carat gold (2004), anodising (2000), sodium under kerosene (1998), coke in the blast furnace (1998), rusting and weight (1980), ionic compounds (2003) and heat conduction by copper (2001).
- GS3 — science, industry and environment: mining and metallurgy (roasting releases sulphur dioxide), the cost of corrosion and its prevention, recycling metals, and India's metallurgical heritage (the Delhi iron pillar — also GS1 culture).
| Word | What it means here |
|---|---|
| Malleable / ductile | Can be beaten into sheets / drawn into wires |
| Sonorous | Rings when struck — why school bells are metal |
| Allotrope | One of the different forms of the same element, e.g. diamond and graphite (carbon) |
| Amphoteric oxide | A metal oxide that reacts with both acids and bases to give salt and water (Al2O3, ZnO) |
| Reactivity (activity) series | Metals listed from most to least reactive, built from displacement experiments |
| Ionic (electrovalent) compound | Formed by transfer of electrons from a metal to a non-metal; made of ions, not molecules |
| Mineral / ore / gangue | Naturally occurring element or compound / a mineral rich enough to extract a metal profitably / the soil and sand mixed with it |
| Roasting / calcination | Strong heating of a sulphide ore in excess air / of a carbonate ore in limited air — both give the oxide |
| Metallurgy | Extracting metals from ores and refining them for use |
| Corrosion | Slow eating away of a metal surface by air, moisture and other chemicals (rust on iron) |
| Alloy | A homogeneous mixture of two or more metals, or a metal and a non-metal; an amalgam contains mercury |
Reading NCERT's chapter opening (page 37)A small drawing of a tank with two plates in a liquid and a brown deposit at the bottom (the refining cell of Figure 3.12 in miniature), a QR code, and three prompts: think of uses of metals and non-metals, the properties you used to sort them, and how those properties relate to the uses. The point: properties decide uses — copper for wires, aluminium for foil, gold for jewellery.
Common confusions
- Metal ≠ ‘hard and shiny’. Sodium is soft enough to cut with a knife; mercury is a liquid; iodine, a non-metal, is shiny.
- Mineral ≠ ore. Every ore is a mineral, but a mineral is an ore only where the metal can be extracted profitably.
- Ionic ≠ covalent. Ionic bonds come from transfer of electrons (metal + non-metal, this chapter); covalent bonds from sharing (mostly non-metals, next chapter).
At a glance — the six ideas to carry away
- Physical properties: metals are lustrous, hard, malleable, ductile, sonorous and good conductors; non-metals are mostly dull, brittle and poor conductors. Exceptions: mercury (liquid metal), bromine (liquid non-metal), soft Li/Na/K, lustrous iodine, conducting graphite, very hard diamond.
- With oxygen: metal + O2 → basic oxide; Al2O3 and ZnO are amphoteric (react with acids and bases). Na2O and K2O dissolve to give alkalis. Na and K are kept under kerosene; Mg, Al, Zn, Pb carry a protective oxide layer; Ag and Au do not react even when hot.
- With water: K, Na violently (H2 catches fire); Ca gently; Mg with hot water; Al, Fe, Zn only with steam; Pb, Cu, Ag, Au not at all. With dilute HCl: Mg > Al > Zn > Fe; copper no reaction. HNO3 gives no H2 (oxidising) except with Mg and Mn when very dilute. Aqua regia (HCl : HNO3 = 3 : 1) dissolves gold.
- Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au. A metal displaces any metal below it from its salt solution; metals above H displace hydrogen from dilute acids.
- Ionic compounds form by electron transfer: Na (2,8,1) → Na+; Cl (2,8,7) → Cl−. They are hard, brittle solids with high melting points (NaCl 1074 K; CaO 2850 K), soluble in water but not in kerosene or petrol, and conduct only when molten or dissolved.
- Metallurgy: ore → remove gangue → (low: heat alone; medium: roast sulphides in excess air or calcine carbonates in limited air, then reduce with carbon or Al — thermit; high: electrolysis of molten compounds) → electrolytic refining (anode impure, cathode pure, anode mud). Rust needs air and water; prevention by paint, grease, galvanising, chrome plating, anodising, alloys.
1. Physical properties: metals vs non-metals
In simple wordsThink of metals as a team in the same uniform: shiny, tough, bendable, ringing when struck, and passing on heat and electricity. Non-metals are a mixed crowd — gases, a crumbly yellow solid, a shiny purple-black one. But every team has players who break the dress code, and that is why the uniform alone cannot settle who belongs.
NCERT tests metals — iron, copper, aluminium, magnesium, sodium, lead, zinc — in six short activities. Rubbed with sandpaper, each shows a shining surface: metallic lustre (Activity 3.1). Most are hard to cut, but sodium — handled with tongs and dried between filter paper — cuts with a knife (3.2). Hammering flattens them: malleability; gold and silver are the most malleable (3.3). Drawing into wires is ductility; gold is the most ductile — about 2 km of wire from one gram (3.4). A wire heated near its clamp soon melts the wax holding a pin at its far end, but the wire itself does not melt: metals are good conductors of heat with high melting points (3.5); silver and copper conduct heat best, lead and mercury comparatively poorly. A bulb in a circuit glows when a metal bridges the gap: metals conduct electricity (3.6) — which is why wires carry a PVC or rubber-like coat. Metals that ring when struck are sonorous.
Non-metals are fewer — carbon, sulphur, iodine, oxygen, hydrogen and so on — and are solids or gases; bromine is the one liquid. Repeating the tests with coal or graphite, sulphur and iodine (Activity 3.7) fills Table 3.1. The lesson: physical properties alone cannot sort elements. All metals except mercury are solids at room temperature; gallium and caesium melt on a palm; iodine is lustrous; carbon exists as allotropes — diamond, the hardest natural substance with very high melting and boiling points, and graphite, which conducts electricity; the alkali metals (lithium, sodium, potassium) are soft, with low densities and low melting points. Chemical properties classify more clearly.
⤵ Sorting an unknown solid with a hammer and a circuit (Activities 3.3, 3.6; exercise 5)
Strike it on an iron blockflattens into a sheet → malleable, likely a metal; shatters → brittle, likely a non-metal
Put it between the clips of a battery–bulb circuitbulb glows → conductor, likely a metal; stays dark → likely a non-metal
Check the exceptionsgraphite conducts though a non-metal; sodium is soft — so a single test can mislead
Confirm with chemistryburn it and test the oxide in water with litmus (Activity 3.8): basic → metal, acidic → non-metal
Reading NCERT's Activities 3.1–3.5 and Figure 3.1 (pages 37–38)Figure 3.1 shows a metal wire held horizontally in a clamp on a stand, a burner heating it near the clamp, and a pin stuck with wax at the free end. The point: heat travels along the metal until the wax melts and the pin drops — metals conduct heat — yet the wire stays solid, showing a high melting point.
Reading NCERT's Activity 3.6, Figure 3.2, Activity 3.7 and Table 3.1 (page 39)Figure 3.2: a battery, a bulb and a switch wired in a loop with two clips, A and B, and an arrow ‘insert sample to be tested’ between them. Table 3.1 is a blank grid with columns for element, symbol, type of surface, hardness, malleability, ductility, electrical conductivity and sonority. The point: one simple circuit separates conductors from non-conductors; the table makes you see that the columns rarely agree perfectly for non-metals.
| Sample (Table 3.1, expected) | Surface | Hardness | Malleable / ductile | Conducts electricity | Sonorous |
|---|---|---|---|---|---|
| Iron, copper, aluminium | lustrous when cleaned | hard | yes / yes | yes | yes |
| Magnesium | lustrous when cleaned | fairly hard | yes / yes | yes | yes |
| Sodium | lustrous when freshly cut | soft (knife cuts it) | — | yes | — |
| Carbon: coal / graphite | dull / greyish-shiny | brittle | no / no | coal no; graphite yes | no |
| Sulphur | dull yellow | brittle | no / no | no | no |
| Iodine | lustrous (an exception) | brittle | no / no | no | no |
Common confusions
- Most malleable: gold and silver; most ductile: gold. Best heat conductors: silver and copper; poor: lead and mercury.
- Mercury is the liquid metal; bromine the liquid non-metal. Gallium and caesium are solids that melt in the hand (low melting points), not liquids.
- Graphite conducts electricity; diamond, another form of the same carbon, does not (Beyond NCERT for diamond's conduction).
- A coated electric wire: the copper inside conducts; the PVC outside insulates for safety.
Beyond NCERT
- Gallium melts at about 29.8 °C and caesium at about 28.4 °C, both below body temperature (about 37 °C) — hence ‘melts in the palm’.
- Carbon's other allotropes include fullerenes (C60) and graphene (a single layer of graphite) — the next chapter touches on them.
- Metalloids such as silicon and germanium sit between metals and non-metals; they are the semiconductors of electronics.
Why this matters for Prelims‘Which non-metal conducts?’, ‘which metal is liquid?’, ‘most ductile metal?’ and alloy-property questions are built from this section; UPSC 2001 asked why heated copper feels hotter than glass at the same temperature — heat conduction (see the answer-key note in Strategy).
2. Metals with oxygen: basic and amphoteric oxides
In simple wordsOxygen is a restless partner. Highly reactive metals grab it so eagerly that they catch fire in open air; others pull on a thin oxide jacket that then protects them; gold and silver ignore it even in a flame. What forms — the oxide — tells you which side of the fence the element sits on: metal oxides behave like bases, non-metal oxides like acids.
In Activity 3.8, burnt magnesium ribbon leaves an ash that dissolves to a solution turning red litmus blue (basic), while the fumes of burning sulphur dissolve to a solution turning blue litmus red (acidic): 2Mg + O2 → 2MgO, MgO + H2O → Mg(OH)2; S + O2 → SO2, SO2 + H2O → H2SO3 (equations Beyond NCERT — the activity asks you to write them). Most non-metals give acidic oxides; most metals give basic oxides. In Activity 3.9 (teacher's help, eye protection), metals are held in a flame with tongs. Almost all form oxides — metal + oxygen → metal oxide: 2Cu + O2 → 2CuO (black copper(II) oxide); 4Al + 3O2 → 2Al2O3.
Amphoteric oxides. Metal oxides are basic, but aluminium oxide and zinc oxide react with both acids and bases to give salt and water: Al2O3 + 6HCl → 2AlCl3 + 3H2O; Al2O3 + 2NaOH → 2NaAlO2 + H2O (sodium aluminate). For zinc oxide (Beyond NCERT equations): ZnO + 2HCl → ZnCl2 + H2O; ZnO + 2NaOH → Na2ZnO2 + H2O. Most metal oxides are insoluble in water, but sodium and potassium oxides dissolve to give alkalis: Na2O(s) + H2O(l) → 2NaOH(aq); K2O(s) + H2O(l) → 2KOH(aq).
Different metals, different appetites. Potassium and sodium react so vigorously that they catch fire in the open, so they are kept under kerosene. At ordinary temperature magnesium, aluminium, zinc and lead carry a thin protective oxide layer that stops further oxidation. Iron does not burn on heating, but iron filings sprinkled into a flame burn vigorously. Copper does not burn but the hot metal is coated with black copper(II) oxide. Silver and gold do not react with oxygen even at high temperatures. Sodium is the most reactive of the samples, magnesium less so; burning cannot rank zinc, iron, copper and lead — that needs more reactions.
⤵ Is the oxide basic or acidic? (Activity 3.8)
Burn magnesium ribbondazzling white flame; white ash 2Mg + O₂ → 2MgO
Dissolve the ash in waterMgO + H₂O → Mg(OH)₂
Litmusred → blue: a basic oxide — metal
Burn sulphur powdercollect the fumes in an inverted test tube S + O₂ → SO₂
Shake with a little waterSO₂ + H₂O → H₂SO₃
Litmusblue → red: an acidic oxide — non-metal
Rulemetals → basic oxides (Al₂O₃, ZnO amphoteric); non-metals → acidic (or neutral) oxides
Reading NCERT's Activities 3.8–3.9 and the ‘Questions’ box (pages 40–41)Two activities without figures — burning magnesium and sulphur and testing the products with litmus; burning metal samples in a flame and ranking them by reactivity towards oxygen. The Questions box asks for a metal that is liquid at room temperature, one easily cut with a knife, the best conductor of heat and a poor one, and the meanings of malleable and ductile. The point: the oxide's nature is the first chemical test that separates metals from non-metals (answers in the in-text section).
Reading NCERT's ‘Do You Know?’ on anodising (page 42)Aluminium's thin natural oxide coat already resists corrosion; anodising makes it thicker. A clean aluminium article is made the anode and electrolysed with dilute sulphuric acid; oxygen released at the anode reacts with the aluminium to build the protective layer, which can also be dyed for an attractive finish. The point: a metal's own oxide can be its armour — UPSC 2000 asked exactly what anodising deposits (aluminium oxide).
⤵ Anodising an aluminium article (‘Do You Know?’, page 42)
Clean the aluminium articleit already has a thin natural oxide layer
Make it the anodeelectrolyse in dilute sulphuric acid
Oxygen is evolved at the anodeit reacts with aluminium — a thicker Al₂O₃ layer forms
Dye (optional) and seala corrosion-resistant, coloured finish (sealing step Beyond NCERT)
Common confusions
- Amphoteric = Al2O3 and ZnO in NCERT. They are metal oxides that also act as acids — not non-metal oxides.
- Sodium is stored under kerosene because it reacts with oxygen and moisture and can catch fire — not because it ‘melts in air’ (UPSC 1998).
- Aluminium is very reactive yet used for cooking pans: its oxide layer protects it (exercise 12c).
- Anodising thickens aluminium's own oxide; it does not coat aluminium with another metal (that would be plating).
- ‘Burning’ in NCERT is not the only test: iron filings burn in a flame although an iron block does not — surface area matters.
Beyond NCERT
- Neutral oxides of non-metals — carbon monoxide (CO), nitrous oxide (N2O) — show neither acidic nor basic behaviour; that is why NCERT's summary says non-metal oxides are ‘acidic or neutral’.
- Flame colours: sodium compounds give a golden-yellow flame, potassium lilac, barium green, copper blue-green — the basis of fireworks colours (UPSC 1989, 2004 asked strontium and barium).
- The same oxide-layer idea is called passivation; chromium in stainless steel forms such a layer.
Why this matters for PrelimsSodium under kerosene (1998) and anodising (2000) are direct from this section; amphoteric oxides and ‘aluminium is reactive yet used for utensils’ are classic statement material.
3. Metals with water and with acids
In simple wordsDrop different metals into water and you get a scale of temperaments: some explode into flame, some fizz politely, some need a hot bath or even steam to react, and some sit there for ever. Dilute acid works the same way, only faster. The order of temperaments is the same each time — that is the clue to the reactivity series.
Water (Activity 3.10, teacher's help): metals react with water to give a metal oxide and hydrogen; a soluble oxide then gives a metal hydroxide. Potassium and sodium react violently with cold water; the reaction is so exothermic that the hydrogen catches fire: 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy; 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) + heat energy. Calcium reacts less violently — the hydrogen does not ignite — and the metal starts floating because hydrogen bubbles cling to it: Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g). Magnesium does not react with cold water but does with hot water, giving magnesium hydroxide and hydrogen, and also floats (Mg + 2H2O → Mg(OH)2 + H2, equation Beyond NCERT). Aluminium, iron and zinc react only with steam, giving the oxide and hydrogen: 2Al(s) + 3H2O(g) → Al2O3(s) + 3H2(g); 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g). Lead, copper, silver and gold do not react with water at all.
⤵ Ranking metals with water (Activity 3.10)
Cold waterK and Na — violent, hydrogen catches fire; Ca — gentle, floats on its bubbles
Hot water, for those that did not reactMg — reacts and floats
Steam (Figure 3.3 set-up)Al, Fe, Zn — 3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)
No reaction even with steamPb, Cu, Ag, Au
Order with waterK > Na > Ca > Mg > Al, Zn, Fe > Pb, Cu, Ag, Au
Reading NCERT's Activity 3.10 and Figure 3.3 — action of steam on a metal (pages 42–43)A horizontal boiling tube held on a stand: at its closed end glass wool soaked in water over a burner, then the metal sample; a cork and delivery tube lead into a trough of water, where an inverted gas jar collects hydrogen gas by displacing water. The point: heating the wet glass wool makes steam, which passes over the hot metal — only then do aluminium, iron and zinc give hydrogen.
Dilute acids (Activity 3.11 — sodium and potassium are left out as too dangerous): samples in dilute hydrochloric acid, each with a thermometer. Bubbles form fastest with magnesium, which also gives the highest temperature; reactivity falls in the order Mg > Al > Zn > Fe; copper gives no bubbles and no temperature change — it does not react with dilute HCl. The equations (asked for in the activity): Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g); 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g); Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g); Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g). Nitric acid is different: it is a strong oxidising agent, so it oxidises the hydrogen to water and is itself reduced to nitrogen oxides (N2O, NO, NO2); only magnesium and manganese give hydrogen with very dilute HNO3.
Reading NCERT's Activity 3.11 and the ‘Do You Know?’ on aqua regia (page 44)Activity 3.11 has no figure: thermometers in test tubes of dilute HCl measure how hot each reaction gets. The box: aqua regia (Latin, ‘royal water’) is a freshly prepared mixture of concentrated hydrochloric and nitric acids in the ratio 3 : 1; it dissolves gold (and platinum), which neither acid can do alone, and is highly corrosive and fuming. The point: ‘unreactive’ gold is not untouchable — this is the key to exercise 15 (the fake goldsmith).
Common confusions
- Calcium and magnesium float because hydrogen bubbles stick to them — not because they are lighter than water in NCERT's explanation.
- Iron + steam gives Fe3O4, not Fe2O3; aluminium + steam gives Al2O3.
- Nitric acid gives no hydrogen with metals (except Mg and Mn with very dilute acid) — a favourite exception.
- Aqua regia is 3 HCl : 1 HNO3, both concentrated — not the reverse.
- With dilute acid the most reactive metal tested is magnesium (Na and K were never tried).
Beyond NCERT
- In aqua regia, nitric acid oxidises gold while chloride ions from hydrochloric acid hold the gold in solution as a complex ion (chloroauric acid) — together they do what neither can alone.
- Lead stands just above hydrogen, but its reaction with dilute HCl soon stops because insoluble lead chloride coats the metal.
Why this matters for PrelimsWhich metals react with cold water, steam or not at all; why nitric acid gives no hydrogen; and the composition of aqua regia are short factual items that recur in science papers and state PSCs.
4. Displacement and the reactivity series
In simple wordsA displacement reaction is a game of musical chairs. A salt solution has a metal sitting in the ‘chair’. If a stronger (more reactive) metal walks in, it takes the chair and the weaker one is pushed out as solid metal. If a weaker metal walks in, nothing happens. Line metals up by who can push out whom and you have the reactivity series.
In Activity 3.12, a clean copper wire goes into iron sulphate solution and an iron nail into copper sulphate solution; after 20 minutes only the iron nail has reacted — it is coated reddish-brown with copper and the blue solution fades: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s). So iron is more reactive than copper. Reactive metals displace less reactive metals from their compounds in solution or molten form: Metal A + salt solution of B → salt solution of A + metal B, if A is more reactive than B. Because not every metal reacts with oxygen, water or acids, displacement gives better evidence. From Activities 1.9 and 3.12 comes Table 3.2, the reactivity or activity series.
⤵ Who displaces whom? (Activity 3.12)
Iron nail in copper sulphate; copper wire in iron sulphateleave for 20 minutes
Iron nail tubebrown copper coats the nail; blue fades — Fe + CuSO₄ → FeSO₄ + Cu
Copper wire tubeno change — copper cannot displace iron
Conclusioniron is more reactive than copper — a displacement reaction ranks them
Repeat with many pairsthe ranking becomes Table 3.2, the activity series
Reading NCERT's Figure 3.4 — reaction of metals with salt solutions (page 45)A wooden test-tube stand holds two corked tubes: one with an iron nail hung by a thread in blue copper sulphate solution, the other with a copper wire in pale iron sulphate solution; a hand below holds up a nail coated brown. The point: the brown coat is copper deposited on iron — visible proof that the reaction went one way only.
Reading NCERT's Table 3.2 — activity series (page 45)Thirteen entries from potassium (most reactive) through sodium, calcium, magnesium, aluminium, zinc, iron, lead, [hydrogen], copper, mercury and silver to gold (least reactive), with a downward arrow ‘reactivity decreases’. Hydrogen is in brackets because it is a non-metal placed for comparison. The point: metals above hydrogen displace it from dilute acids; metals below do not (the chapter summary).
| Metal (page 46 puzzle) | Iron(II) sulphate | Copper(II) sulphate | Zinc sulphate | Silver nitrate | So it sits… |
|---|---|---|---|---|---|
| A | no reaction | displacement | — | — | between Fe and Cu |
| B | displacement | — | no reaction | — | between Zn and Fe |
| C | no reaction | no reaction | no reaction | displacement | between Cu and Ag |
| D | no reaction | no reaction | no reaction | no reaction | below Ag |
Reading NCERT's ‘Questions’ box with its results table (page 46)Five questions: why sodium is kept in kerosene; equations for iron with steam and for calcium and potassium with water; the A–D puzzle (table above — NCERT leaves some cells blank); which gas forms when dilute HCl meets a reactive metal, with the equation for iron and dilute H2SO4; and what happens when zinc is added to iron(II) sulphate. The point: every answer comes from the series — the puzzle order is B > A > C > D (checked against every filled cell in this page's source).
Common confusions
- Displacement needs the more reactive metal as the solid and the less reactive one in the salt: Fe + CuSO4 works, Cu + FeSO4 does not.
- Cu + AgNO3 does react (copper is above silver) — exercise 1(d); Al + MgCl2 does not (aluminium is below magnesium).
- [H] is not a metal; it is in the list only to show which metals release hydrogen from dilute acids.
- The colour change in the iron-nail tube is blue → pale green (iron(II) sulphate), not blue → colourless.
Beyond NCERT
- The fuller series in higher classes is based on standard electrode potentials; lithium sits at the very top. NCERT's 13-entry list is enough for school and Prelims.
- Displacement is used industrially: copper is recovered from dilute leach solutions by passing them over scrap iron (‘cementation’).
Why this matters for PrelimsGalvanising, tin cans, sacrificial protection, why copper vessels are cleaned with tamarind, and which metals give hydrogen with acid are all reactivity-series reasoning. Learn the 13-step order by heart.
5. Why metals react: electrons, ions and ionic bonds
In simple wordsAtoms are happiest with a full outer shell, like the noble gases. A sodium atom has one extra electron it would gladly give away; a chlorine atom is one short. When they meet, sodium hands over its spare electron. Now sodium is a positive ion and chlorine a negative one — and opposite charges cling to each other. That handshake is an ionic bond.
Noble gases, with completely filled valence shells, show little chemical activity, so reactivity is explained as a tendency to attain a completely filled valence shell. Table 3.3 lists configurations: a sodium atom (2, 8, 1) loses its one M-shell electron, leaving a stable octet in the L shell; with 11 protons and now 10 electrons it becomes the sodium cation Na+: Na → Na+ + e−. A chlorine atom (2, 8, 7) gains one electron; with 17 protons and 18 electrons it becomes the chloride anion Cl−: Cl + e− → Cl−. The oppositely charged ions are held by strong electrostatic forces as sodium chloride — which exists not as molecules but as aggregates of ions. For magnesium chloride, Mg → Mg2+ + 2e−, and the two electrons go to two chlorine atoms, giving Mg2+ and 2Cl−. Compounds formed by transfer of electrons from a metal to a non-metal are ionic or electrovalent compounds.
| Type (Table 3.3) | Element | Atomic number | Electrons in K, L, M, N | To reach a full shell (our column) |
|---|---|---|---|---|
| Noble gas | Helium (He) | 2 | 2 | full outer shell — little activity |
| Noble gas | Neon (Ne) | 10 | 2, 8 | full outer shell — little activity |
| Noble gas | Argon (Ar) | 18 | 2, 8, 8 | full outer shell — little activity |
| Metal | Sodium (Na) | 11 | 2, 8, 1 | loses 1 → Na+ |
| Metal | Magnesium (Mg) | 12 | 2, 8, 2 | loses 2 → Mg2+ |
| Metal | Aluminium (Al) | 13 | 2, 8, 3 | loses 3 → Al3+ |
| Metal | Potassium (K) | 19 | 2, 8, 8, 1 | loses 1 → K+ |
| Metal | Calcium (Ca) | 20 | 2, 8, 8, 2 | loses 2 → Ca2+ |
| Non-metal | Nitrogen (N) | 7 | 2, 5 | gains 3 → N3− |
| Non-metal | Oxygen (O) | 8 | 2, 6 | gains 2 → O2− |
| Non-metal | Fluorine (F) | 9 | 2, 7 | gains 1 → F− |
| Non-metal | Phosphorus (P) | 15 | 2, 8, 5 | gains 3 → P3− |
| Non-metal | Sulphur (S) | 16 | 2, 8, 6 | gains 2 → S2− |
| Non-metal | Chlorine (Cl) | 17 | 2, 8, 7 | gains 1 → Cl− |
⤵ How sodium chloride forms (Figure 3.5)
Sodium atom, 2, 8, 1one electron beyond a stable octet
It loses that electronNa → Na⁺ + e⁻ — 11 protons, 10 electrons
Chlorine atom, 2, 8, 7, takes itCl + e⁻ → Cl⁻ — 17 protons, 18 electrons
Opposite charges attractstrong electrostatic forces hold Na⁺ and Cl⁻ together as an ionic solid, not molecules
Reading NCERT's Table 3.3 and Figure 3.5 (page 47)Table 3.3 gives atomic numbers and K-L-M-N electron counts for three noble gases (He, Ne, Ar), five metals (Na, Mg, Al, K, Ca) and six non-metals (N, O, F, P, S, Cl). Figure 3.5 writes the two half-changes — Na (2,8,1) → Na+ (2,8) + e−, and Cl (2,8,7) + e− → Cl− (2,8,8) — then an electron-dot picture: a dot from Na moving by a curved arrow to Cl's ring of crosses, giving (Na+) and [Cl]−. The point: metals have 1–3 outer electrons to lose, non-metals 5–7 and gain — checked for every row in this page's source.
Reading NCERT's Figure 3.6 — formation of magnesium chloride (page 48)Mg (2,8,2) → Mg2+ (2,8) + 2e−; each of two Cl atoms takes one electron; the dot picture shows two curved arrows from Mg to two Cl atoms and the product (Mg2+)[Cl]−2. The point: the formula MgCl2 follows from charge balance — one 2+ ion needs two 1− ions. The text asks you to name the ions: Mg2+ and Cl−.
Common confusions
- Cation = positive (metals lose electrons); anion = negative (non-metals gain). Losing electrons makes an atom positive, not negative.
- The nucleus does not change: Na+ still has 11 protons; only the electron count changes.
- ‘NaCl molecule’ is wrong: an ionic solid is a lattice of ions.
- NCERT slip: page 47 prints the chloride ion as ‘C1–’ (with the digit one) — read Cl−.
- Ionic (transfer, metal + non-metal) vs covalent (sharing, non-metals): the next chapter.
Beyond NCERT
- Loss of electrons is oxidation and gain is reduction (Class 11 definition) — so forming NaCl oxidises sodium and reduces chlorine, linking this section to Chapter 1's redox.
- The number of electrons an atom loses or gains is its valency in the ionic compound (Na 1, Mg 2, Al 3; Cl 1, O 2).
Why this matters for PrelimsElectron transfer explains why the alkali metals are so reactive and why sodium is never found free — the logic behind questions on storage, occurrence and extraction.
6. Properties of ionic compounds
In simple wordsAn ionic solid is like a crowd in a stadium, every seat locked, with plus and minus fans glued to their neighbours. It takes a lot of energy (heat) to break them free — so the melting point is high. Locked in their seats they cannot carry current; melt the solid or dissolve it in water and the fans can move — now it conducts.
In Activity 3.13, salts such as sodium chloride, potassium iodide and barium chloride are examined: their state, what happens when heated on a spatula in a flame (Figure 3.7), whether they dissolve in water, petrol and kerosene, and whether their solutions light a bulb (Figure 3.8). The general properties: (i) physical nature — solids, somewhat hard because of strong attraction between ions, generally brittle, breaking under pressure; (ii) high melting and boiling points — much energy is needed to break the inter-ionic attraction (Table 3.4); (iii) solubility — generally soluble in water, insoluble in kerosene and petrol; (iv) conduction — they conduct in solution and when molten, because the ions can move to the oppositely charged electrodes, but not as solids, where the rigid structure holds the ions in place.
| Ionic compound (Table 3.4) | Melting point (K) | Boiling point (K) | Melting point in °C (Beyond NCERT conversion) |
|---|---|---|---|
| NaCl | 1074 | 1686 | about 801 °C |
| LiCl | 887 | 1600 | about 614 °C |
| CaCl2 | 1045 | 1900 | about 772 °C |
| CaO | 2850 | 3120 | about 2577 °C |
| MgCl2 | 981 | 1685 | about 708 °C |
⤵ Testing an ionic compound (Activity 3.13)
Look at ita crystalline solid
Heat a little on a spatula in a flame (Fig. 3.7)it does not melt easily; the flame may take a colour
Try three solventsdissolves in water; not in petrol or kerosene
Dip graphite electrodes in its solution (Fig. 3.8)the bulb glows — ions carry the current
Inferencean ionic compound: hard, high-melting, water-soluble, conducts when dissolved or molten
Reading NCERT's Activity 3.13, Figures 3.7–3.8 and Table 3.4 (page 48)Figure 3.7: a hand holds a spatula containing a sample over a burner flame. Figure 3.8: a beaker of salt solution under test with two graphite rods wired through a battery, bulb and switch. Table 3.4 gives melting and boiling points in kelvin for NaCl, LiCl, CaCl2, CaO and MgCl2. The point: every listed compound melts above 880 K, and CaO — with doubly charged ions — is highest at 2850 K (both checked in this page's source).
Reading NCERT's ‘Questions’ box (page 49)Two questions: (1) write electron-dot structures for sodium, oxygen and magnesium, show the formation of Na2O and MgO by electron transfer, and name the ions; (2) why ionic compounds have high melting points. The point: the same transfer logic as NaCl, with oxygen taking two electrons (outlines in the in-text section).
Common confusions
- Solid ionic compounds do not conduct; molten or dissolved ones do. (UPSC 2003: ‘ionic compounds in the solid state are good conductors’ — false.)
- Ionic compounds are hard but brittle — not malleable like metals.
- ‘Insoluble in kerosene and petrol’ is NCERT's statement; alcohol is not mentioned. Many ionic compounds dissolve poorly in alcohol, but some (e.g. calcium chloride) dissolve well — Beyond NCERT nuance behind UPSC 2003's statement 1.
- Table 3.4 is in kelvin; subtract 273 for °C (NaCl melts at 801 °C).
Beyond NCERT
- Water dissolves ionic solids because its polar molecules surround and stabilise the separated ions (UPSC 1994 asked this as ‘high dipole moment’).
- Molten-salt conduction is exactly what electrolytic extraction (Section 8) exploits: molten NaCl conducts, and sodium collects at the cathode.
Why this matters for PrelimsStatement questions on ionic compounds (2003) test solubility and conduction — the four properties above, stated precisely, are enough.
7. Where metals come from: minerals, ores and the route to a metal
In simple wordsThe reactivity series is also a map of where metals hide. Lazy metals like gold lie around uncombined; restless ones like sodium are always locked in compounds. The more tightly a metal is locked, the more force it takes to free it — gentle heat for the lazy ones, carbon for the middle ones, electricity for the restless ones.
The earth's crust is the main source of metals; seawater holds soluble salts such as sodium and magnesium chlorides. Naturally occurring elements or compounds are minerals; minerals with a high enough percentage of a metal to extract it profitably are ores. Metals at the bottom of the series — gold, silver, platinum, copper — occur free (copper and silver also as sulphide or oxide ores). Those at the top (K, Na, Ca, Mg, Al) are never found free. Those in the middle (Zn, Fe, Pb) occur mainly as oxides, sulphides or carbonates. Many ores are oxides because oxygen is very reactive and abundant. Mined ore carries gangue — soil, sand and other impurities — removed first by methods based on differences in physical or chemical properties (enrichment). Then the metal is extracted by a route chosen by its reactivity (Figure 3.9), and finally refined.
Reading NCERT's Figure 3.9 — activity series and related metallurgy (page 50)Eleven symbols in a column — K, Na, Ca, Mg, Al bracketed ‘Electrolysis’; Zn, Fe, Pb, Cu bracketed ‘Reduction using carbon’; Ag, Au bracketed ‘Found in native state’. The point: position decides method. Note two mismatches with the text: the figure puts copper in the carbon band, while the text lists copper among metals found free and extracts it from Cu2S by heating alone; and it leaves out mercury, the text's example for heating alone.
Reading NCERT's Figure 3.10 — steps in the extraction of metals (page 50)A branching flowchart: Ore → Concentration of ore, then three branches. High reactivity: electrolysis of molten ore → pure metal. Medium: carbonate ore → calcination, sulphide ore → roasting, both → oxide of metal → reduction to metal → purification. Low: sulphide ore → roasting → metal → refining. The point: concentration first, refining last, and the middle step depends on reactivity — redrawn above in our own layout.
Reading NCERT's ‘Questions’ box (page 53)Three questions: define mineral, ore and gangue; name two metals found free in nature; and name the chemical process that gets a metal from its oxide (reduction). The point: the definitions are exam-ready one-liners (outlines in the in-text section).
Common confusions
- All ores are minerals; not all minerals are ores — profitability decides.
- Gangue is the unwanted rock mixed with ore — removed before extraction; slag (Beyond NCERT) is what forms during smelting when a flux reacts with gangue.
- NCERT inconsistency: Figure 3.9 places Cu with carbon reduction; the text says copper occurs free and is got from Cu2S by heating alone. Safe exam line: copper is a low-reactivity metal, extracted from its sulphide ore by roasting/self-reduction; answer ‘reduction using carbon’ only if a question quotes Figure 3.9.
- Top-of-series metals: ‘never found free’ — K, Na, Ca, Mg, Al.
Beyond NCERT — common ores
- Bauxite (aluminium), haematite and magnetite (iron), galena (lead), zinc blende and calamine (zinc), cinnabar (mercury — NCERT names it), copper glance (Cu2S), argentite (silver). UPSC matched ores to metals in 1980, 1983, 1985 and 1988 — those questions are tagged to the geography chapters.
- Concentration methods include gravity separation, froth flotation (for sulphide ores) and magnetic separation.
Why this matters for GS3Mining policy, critical minerals and the environmental cost of extraction (tailings, sulphur dioxide from roasting) all rest on this chain: ore → concentration → extraction → refining.
8. Extracting and refining metals
In simple wordsGetting a metal out of its compound is a tug-of-war for oxygen (or sulphur, or chlorine). Heat alone wins for weak holders like mercury. For the middle metals you bring in a stronger puller — carbon, or a more reactive metal such as aluminium. For the strongest holders nothing chemical is strong enough, so you use electricity. Then you clean up the metal by moving it, atom by atom, from a dirty block to a pure strip.
Low in the series: oxides of very unreactive metals are reduced by heating alone. Cinnabar (HgS), an ore of mercury, heated in air gives mercuric oxide, which on further heating gives mercury: 2HgS(s) + 3O2(g) —[heat]→ 2HgO(s) + 2SO2(g); 2HgO(s) —[heat]→ 2Hg(l) + O2(g). Copper from Cu2S, by heating in air: 2Cu2S + 3O2(g) —[heat]→ 2Cu2O(s) + 2SO2(g); 2Cu2O + Cu2S —[heat]→ 6Cu(s) + SO2(g).
⤵ Mercury from cinnabar — heat alone (page 51)
Cinnabar, HgSa sulphide ore of mercury, a low-reactivity metal
Heat in air2HgS(s) + 3O₂(g) —[heat]→ 2HgO(s) + 2SO₂(g)
Heat further2HgO(s) —[heat]→ 2Hg(l) + O₂(g)
Liquid mercuryno carbon, no electricity needed
Middle of the series (iron, zinc, lead, copper): usually sulphides or carbonates. A metal is easier to obtain from its oxide, so first: roasting — heating a sulphide ore strongly in excess air: 2ZnS(s) + 3O2(g) —[heat]→ 2ZnO(s) + 2SO2(g); calcination — heating a carbonate ore strongly in limited air: ZnCO3(s) —[heat]→ ZnO(s) + CO2(g). The oxide is then reduced, e.g. with carbon: ZnO(s) + C(s) → Zn(s) + CO(g). Obtaining a metal from its compounds is a reduction. Besides carbon (coke), highly reactive metals such as sodium, calcium and aluminium can be used as reducing agents, because they displace less reactive metals: 3MnO2(s) + 4Al(s) → 3Mn(l) + 2Al2O3(s) + heat — manganese dioxide is reduced, aluminium oxidised. These reactions are so exothermic that the metal comes out molten; iron(III) oxide with aluminium is the thermit reaction, used to join railway tracks and cracked machine parts: Fe2O3(s) + 2Al(s) → 2Fe(l) + Al2O3(s) + heat.
⤵ Zinc from its ores (page 51)
Sulphide ore ZnS → roastingstrong heat, excess air: 2ZnS + 3O₂ → 2ZnO + 2SO₂
Carbonate ore ZnCO₃ → calcinationstrong heat, limited air: ZnCO₃ → ZnO + CO₂
Zinc oxide is reduced with carbonZnO(s) + C(s) → Zn(s) + CO(g)
Impure zinc is refinedelectrolytically — see below
Reading NCERT's Figure 3.11 — thermit process for joining railway tracks (page 52)A photograph of a worker in protective gear with a crucible set over a rail joint, beside the track. The point: thermit is a field welding method — the reaction needs no outside heat once started, and the molten iron it makes fills the gap between rails. (We describe the photo; it is not reproduced.)
Top of the series: carbon cannot reduce the oxides of sodium, magnesium, calcium or aluminium, because these metals have more affinity for oxygen than carbon. They are obtained by electrolytic reduction: sodium, magnesium and calcium by electrolysis of their molten chlorides, the metal depositing at the cathode (negative) and chlorine at the anode (positive) — at the cathode Na+ + e− → Na, at the anode 2Cl− → Cl2 + 2e−. Aluminium is obtained by electrolytic reduction of aluminium oxide.
Refining. Metals from these processes are not very pure. The most widely used method is electrolytic refining — for copper, zinc, tin, nickel, silver, gold and others. The impure metal is the anode, a thin strip of pure metal the cathode, and a solution of the metal's salt the electrolyte. Current makes metal from the anode dissolve into the electrolyte and an equal amount of pure metal deposit on the cathode; soluble impurities stay in solution and insoluble impurities settle below the anode as anode mud. For copper (half-equations Beyond NCERT): anode Cu(s) → Cu2+(aq) + 2e−; cathode Cu2+(aq) + 2e− → Cu(s).
⤵ Electrolytic refining of copper (Figure 3.12)
Set up the cellanode: impure copper block · cathode: thin pure-copper strip · electrolyte: acidified copper sulphate solution
Pass currentanode copper dissolves: Cu → Cu²⁺ + 2e⁻
Cu²⁺ ions move to the cathodepure copper deposits: Cu²⁺ + 2e⁻ → Cu
Soluble impuritiesstay dissolved in the electrolyte
Insoluble impuritiesfall below the anode as anode mud
Reading NCERT's Figure 3.12 — electrolytic refining of copper (page 52)A tank of acidified copper sulphate solution; a thin cathode (−) on the left, a thick anode (+) on the right, joined through a key and a battery; wavy arrows show Cu2+ ions travelling from anode to cathode; a brown heap under the anode is labelled impurities (anode mud). The caption states the electrolyte, anode and cathode. The point: the anode shrinks, the cathode grows, and the waste falls out — exactly what exercise 8 asks.
Common confusions
- Roasting = sulphide ore, excess air, gives SO2; calcination = carbonate ore, limited air, gives CO2. Both end in the metal oxide.
- In refining, the impure metal is the anode (+) and the pure strip the cathode (−) — reversing them is the commonest error.
- In electrolytic extraction, metal collects at the cathode and chlorine at the anode.
- In the thermit reaction aluminium is the reducing agent (it is oxidised); iron(III) oxide is reduced.
- Carbon fails for the top metals because those metals hold oxygen more strongly than carbon does.
- Valuable metals such as silver and gold often turn up in the anode mud when copper is refined (Beyond NCERT).
Beyond NCERT — the blast furnace and aluminium
- In a blast furnace, coke burns as fuel and also makes the reducing agent: C + O2 → CO2; CO2 + C → 2CO; Fe2O3 + 3CO → 2Fe + 3CO2. Limestone is the flux that removes silica: CaCO3 —[heat]→ CaO + CO2, CaO + SiO2 → CaSiO3 (slag). So coke reduces and supplies heat; it does not remove silica and is not an oxidising agent (UPSC 1998).
- Aluminium is made by electrolysing alumina dissolved in molten cryolite (the Hall–Héroult process); overall 2Al2O3 —[electricity]→ 4Al + 3O2. It needs very large amounts of electricity — why aluminium smelters sit near cheap power.
- Molten NaCl electrolysis overall: 2NaCl(l) —[electricity]→ 2Na(l) + Cl2(g).
Why this matters for Prelims and GS3Coke's role (1998), roasting vs calcination, the thermit reaction and the electrodes in refining are standard statement items. For GS3, roasting sulphide ores releases sulphur dioxide — a reason smelters face pollution controls; electrolytic extraction ties metal output to power supply.
9. Corrosion and its prevention
In simple wordsCorrosion is a metal slowly going back to the compound it was extracted from — iron back towards an iron oxide, silver towards a sulphide. Iron needs two things at once to rust: air and water. Take away either and it stays bright. Every method of prevention either builds a wall (paint, grease, another metal) or changes the metal itself (alloys).
From Chapter 1: silver turns black in air by reacting with sulphur compounds to form silver sulphide; copper reacts with moist carbon dioxide in air and gains a green coat of basic copper carbonate; iron in moist air acquires a brown, flaky coating of rust. In Activity 3.14, clean iron nails go into three corked tubes: A with ordinary water (air and water), B with boiled distilled water under about 1 mL of oil (water but no dissolved air), C with anhydrous calcium chloride (dry air). After a few days, only the nails in A rust: iron needs both air (oxygen) and water. Equations for the tarnish and the green coat (Beyond NCERT): 4Ag + 2H2S + O2 → 2Ag2S + 2H2O; 2Cu + H2O + CO2 + O2 → CuCO3·Cu(OH)2.
⤵ What does iron need to rust? (Activity 3.14)
Three tubes, clean iron nails, corkedleave for a few days
A: water + airnails rust
B: boiled water under oilno dissolved air — no rust
C: anhydrous CaCl₂dry air — no rust
Conclusionrusting needs oxygen AND water together; remove either and iron is safe
Reading NCERT's Activity 3.14 and Figure 3.13 (page 53)Three corked tubes labelled A, B and C: A has air above water and rusty iron nails; B has air above a layer of oil that prevents air dissolving in boiled distilled water (boiled to remove dissolved air), with clean nails; C has dry air over anhydrous calcium chloride (drying agent), with clean nails. The point: a controlled experiment — each tube removes one factor, so only A's conditions cause rust.
Prevention. Rusting is prevented by painting, oiling, greasing, galvanising, chrome plating, anodising or making alloys. Galvanisation coats steel and iron with a thin layer of zinc; the article stays protected even if the zinc coat is broken — NCERT asks you to reason why. Zinc is more reactive than iron, so where both are exposed, zinc reacts first (Zn → Zn2+ + 2e−) and the iron is spared.
Common confusions
- Corrosion is the general term; rusting is corrosion of iron only. Silver's black coat is silver sulphide; copper's green coat is basic copper carbonate.
- Rusting needs air and water together; tube B (no air) and tube C (no water) prove each is necessary.
- When iron rusts its mass increases — it gains oxygen and water (UPSC 1980).
- Galvanising = zinc; tinning = tin (food cans); chrome plating = chromium; anodising = thicker aluminium oxide. Galvanised iron is protected even when scratched; tin-plate is not.
- Food cans use tin, not zinc, because zinc is more reactive and would react with food acids (exercise 4).
Beyond NCERT
- Rust is mainly hydrated iron(III) oxide, Fe2O3·xH2O; it is porous and flaky, so unlike aluminium's oxide it does not protect the metal beneath.
- Galvanising is done by dipping iron into molten zinc (hot-dip galvanising — UPSC 1992) or by electroplating zinc.
- Sacrificial protection extends the zinc idea: blocks of zinc or magnesium bolted to ship hulls and buried pipelines corrode instead of the steel. Cathodic protection is the general term.
- Salt water speeds rusting (dissolved ions help the electrochemical reaction) — why coastal and winter-road steel corrodes faster.
Why this matters for Prelims and GS3Galvanising alone has been asked four times (1982, 1983, 1992, 1994), rust and weight once (1980). For GS3, corrosion protection matters to bridges, pipelines, railways and ships — infrastructure maintenance is largely a corrosion problem.
10. Alloys
In simple wordsPure metals are often like plain dough — too soft or too weak for the job. Knead in a little of something else and you get a tougher, more useful mix. A pinch of carbon turns soft iron into steel; nickel and chromium make it stainless; copper or silver makes soft gold hard enough for jewellery.
Alloying is a very good way to improve a metal's properties. Iron is the most widely used metal but never used pure: pure iron is very soft and stretches easily when hot. With a small amount of carbon (about 0.05%) it becomes hard and strong; with nickel and chromium it becomes stainless steel, hard and rust-free. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, made by melting the primary metal, dissolving the others in definite proportions, and cooling. If one metal is mercury, the alloy is an amalgam. The electrical conductivity and melting point of an alloy are lower than those of the pure metals: brass (copper and zinc) and bronze (copper and tin) conduct less well than copper, which is why copper is used for circuits; solder (lead and tin) has a low melting point and is used to join electrical wires.
| Alloy (NCERT) | Made of | Property gained | Use |
|---|---|---|---|
| Steel | iron + a little carbon (about 0.05%, NCERT) | hard and strong | construction, tools |
| Stainless steel | iron + nickel + chromium | hard; does not rust | utensils, cutlery, surgical tools (uses Beyond NCERT) |
| Brass | copper + zinc | conducts less than copper | fittings, utensils (Beyond NCERT) |
| Bronze | copper + tin | conducts less than copper | statues, medals, bells (Beyond NCERT) |
| Solder | lead + tin | low melting point | joining electrical wires |
| Amalgam | mercury + another metal | — | dental fillings (Beyond NCERT) |
| 22-carat gold | 22 parts gold + 2 parts copper or silver | harder than 24-carat | jewellery in India |
Reading NCERT's ‘Do You Know?’ on carat gold (page 54)Pure gold — 24 carat — is very soft and unsuitable for jewellery, so it is alloyed with silver or copper; in India 22 carat is generally used: 22 parts gold with 2 parts copper or silver. The point: carat counts gold in 24ths — 22 carat ≈ 91.67% gold, 18 carat = 18 parts gold + 6 other = 75% (UPSC 2004; percentages computed and checked in this page's source).
Reading NCERT's ‘More to Know!’ — the iron pillar at Delhi (page 54)A photograph of the pillar in a railed enclosure among ruins, with a box headed ‘The wonder of ancient Indian metallurgy’: the iron pillar near the Qutub Minar was made more than 1600 years ago by Indian iron workers who had a process that prevented rusting; scientists worldwide have examined it; it is 8 m high and weighs 6 tonnes (6000 kg). The point: rust resistance is not only a modern achievement.
Common confusions
- Brass = copper + zinc; bronze = copper + tin — the commonest swap. Solder = lead + tin (UPSC 2006).
- Zinc is an element, not an alloy (UPSC 1984, 1989 — ‘which is not an alloy: bronze, brass, steel, zinc’).
- Stainless steel: NCERT says iron + nickel and chromium; all steel also has carbon. UPSC 1980's answer ‘chromium and carbon’ is the only option with chromium — chromium is the essential rust-proofing element.
- Alloys have lower conductivity and melting point than their pure component metals (NCERT's general statement).
- 18 carat = 18 parts gold out of 24, i.e. 18 gold + 6 other, not 18% gold.
- NCERT wording slips: solder is used for soldering (joining at low temperature), not ‘welding’; and brass and bronze do conduct electricity — just less well than copper.
Beyond NCERT
- Stainless steel contains at least about 10.5% chromium, which forms a thin, self-healing chromium oxide layer (passivation).
- The Delhi pillar dates from the Gupta period and carries an inscription of a king ‘Chandra’, usually identified with Chandragupta II. Studies attribute its rust resistance to a high phosphorus content in the wrought iron, which helps a thin protective film form, together with Delhi's relatively dry climate.
- South India's wootz crucible steel was famed in antiquity — a GS1 culture link.
- Mercury from amalgam use in small-scale gold mining is a major source of mercury pollution; the Minamata Convention on Mercury (adopted 2013, in force 2017) aims to curb it.
Why this matters for PrelimsAlloy composition is one of UPSC's most repeated science themes: stainless steel (1980), ‘not an alloy’ (1984, 1989), 18-carat gold (2004), solder (2006). Keep a five-line alloy list ready.
NCERT's in-text questions and activities — short answers
Short outlines in page order, for questions in the running text, the activities and the five ‘Questions’ boxes.
Page 37: Uses of metals and non-metals in daily life; the properties you used to sort them; how properties relate to uses.
Metals: copper and aluminium wires (conduct), iron and steel structures (strong), aluminium foil (malleable), gold jewellery (lustrous, unreactive). Non-metals: oxygen for breathing, carbon (graphite) in pencils, sulphur in matches and medicines, chlorine to disinfect water. Properties used: lustre, hardness, malleability, ductility, conduction, sonority — and each property suits a use.
Activities 3.1–3.2 (page 37): Appearance before and after cleaning? Can the metals be cut with a knife? What about sodium?
Dull before, shiny after rubbing — metallic lustre. Iron, copper, aluminium and magnesium are not cut by a knife; sodium is soft and cuts easily.
Activity 3.3 (page 38): What happens when the metals are hammered?
They flatten into thin sheets without breaking — malleability. Metals are generally hard, but hardness varies.
Activity 3.4 (page 38): List metals whose wires you have seen.
Copper and aluminium (electric wires), iron (fencing, binding wire), silver and gold (jewellery), tungsten (bulb filament — Beyond NCERT). Ductility lets metals be drawn into wires.
Page 38: Which metals are used for cooking vessels, and why?
Aluminium, steel (iron), copper and brass — they are good conductors of heat with high melting points, and malleable enough to shape.
Activity 3.5 (page 38): What do you observe after some time? Does the wire melt?
The wax melts and the pin falls — heat travels along the wire. The wire does not melt: metals conduct heat and have high melting points.
Activity 3.6 (page 39): Does the bulb glow? What does this indicate?
Yes — metals conduct electricity.
Page 39: Why are electric wires coated with PVC or a rubber-like material?
These are insulators: they stop current leaking to people or other wires, preventing shocks and short circuits.
Page 39: Why are school bells made of metals?
Metals are sonorous — they ring when struck.
Activity 3.7 (page 39): Repeat the tests on carbon, sulphur and iodine; fill Table 3.1.
Mostly dull, brittle, not malleable or ductile, non-conducting and not sonorous; but iodine is lustrous and graphite conducts — see the expected table in Section 1.
Activity 3.8 (page 40): Is the product of burning magnesium acidic or basic? Of burning sulphur? Write equations.
Magnesium oxide solution is basic (red litmus → blue): 2Mg + O2 → 2MgO; MgO + H2O → Mg(OH)2. Sulphur dioxide solution is acidic (blue litmus → red): S + O2 → SO2; SO2 + H2O → H2SO3.
Page 40, Q1: Give an example of a metal which (i) is liquid at room temperature (ii) can be easily cut with a knife (iii) is the best conductor of heat (iv) is a poor conductor of heat.
(i) Mercury (ii) sodium (or lithium, potassium) (iii) silver (and copper) (iv) lead (or mercury).
Page 40, Q2: Explain malleable and ductile.
Malleable: can be beaten into thin sheets (gold, silver most). Ductile: can be drawn into thin wires (gold most — about 2 km from one gram).
Activity 3.9 (page 41): Which metals burn easily, with what flame, how does the surface look, what is the order of reactivity, and are the products soluble?
Sodium and magnesium burn easily (magnesium with a dazzling white flame; sodium golden-yellow — Beyond NCERT). Copper does not burn but gets a black CuO coat; iron filings sparkle in a flame. Order towards oxygen: Na > Mg > Zn, Fe, Cu, Pb (the last four cannot be ranked by burning). Most oxides are insoluble; Na2O dissolves to give an alkali.
Page 41: Recall how copper oxide reacts with hydrochloric acid.
As a basic oxide: CuO + 2HCl → CuCl2 + H2O — a blue-green solution (Chapter 2).
Activity 3.10 (page 42): Which metals react with cold water, produce fire, start floating; which react with hot water, steam, or not at all? Order of reactivity?
Cold water: K, Na (violent, hydrogen catches fire), Ca (gentle, floats). Hot water: Mg (floats). Steam: Al, Fe, Zn. None: Pb, Cu, Ag, Au. Order: K > Na > Ca > Mg > Al, Zn, Fe > Pb, Cu, Ag, Au.
Activity 3.11 (page 44): Which metals reacted vigorously with dilute HCl; which gave the highest temperature; order; equations.
Magnesium — fastest bubbles and highest temperature. Order: Mg > Al > Zn > Fe; copper does not react. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g); 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g); Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g); Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g).
Activity 3.12 (pages 44–45): In which tube did a reaction occur, how do you know, what is the equation and the type? Which is more reactive, copper or iron?
In the tube with the iron nail in copper sulphate: the nail gets a brown copper coat and the blue colour fades. Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s) — a displacement reaction. Iron is more reactive than copper, consistent with Activities 3.9–3.11.
Page 46, Q1: Why is sodium kept immersed in kerosene oil?
It reacts so vigorously with oxygen and moisture in air that it can catch fire; kerosene keeps air and water away.
Page 46, Q2: Equations for (i) iron with steam (ii) calcium and potassium with water.
(i) 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
(ii) Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g); 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy
(ii) Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g); 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy
Page 46, Q3: Metals A–D in four salt solutions (table). (i) Most reactive? (ii) B in copper(II) sulphate? (iii) Order of decreasing reactivity?
(i) B — it displaces iron. (ii) B is above iron, so above copper: it displaces copper — a reddish-brown deposit forms and the blue colour fades. (iii) B > A > C > D (B between Zn and Fe; A between Fe and Cu; C between Cu and Ag; D below Ag — every filled cell checked).
Page 46, Q4: Which gas is produced when dilute HCl is added to a reactive metal? Write the reaction of iron with dilute H₂SO₄.
Hydrogen. Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g).
Page 46, Q5: What would you observe when zinc is added to iron(II) sulphate? Write the reaction.
Zinc is above iron, so it displaces iron: the pale green solution becomes colourless and a dark deposit of iron forms on the zinc. Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s).
Page 48: Name the cation and anion in MgCl₂.
Cation Mg2+; anion Cl− (two of them).
Activity 3.13 (page 48): State of the salts; do they melt or colour the flame; solubility in water, petrol, kerosene; conductivity; nature?
Crystalline solids; they do not melt easily (high melting points); the flame takes a colour (Beyond NCERT: sodium yellow, potassium lilac, barium green); soluble in water, insoluble in petrol and kerosene; solutions conduct. They are ionic compounds.
Page 49, Q1: (i) Electron-dot structures of sodium, oxygen and magnesium. (ii) Show the formation of Na₂O and MgO by electron transfer. (iii) Name the ions.
(i) Na: one dot (2,8,1); O: six dots (2,6); Mg: two dots (2,8,2). (ii) Two Na atoms each give one electron to one O atom: 2Na → 2Na+ + 2e−; O + 2e− → O2− → Na2O = 2Na+ + O2−. One Mg gives two electrons to one O: Mg → Mg2+ + 2e−; O + 2e− → O2− → MgO. (iii) Na2O: Na+, O2−; MgO: Mg2+, O2−.
Page 49, Q2: Why do ionic compounds have high melting points?
Strong electrostatic attraction between oppositely charged ions needs a lot of energy to overcome.
Page 52: In 3MnO₂ + 4Al → 3Mn + 2Al₂O₃, which substance is oxidised and which reduced?
Aluminium is oxidised (gains oxygen → Al2O3); manganese dioxide is reduced (loses oxygen → Mn). 3MnO2(s) + 4Al(s) → 3Mn(l) + 2Al2O3(s) + heat
Page 53, Q1: Define (i) mineral (ii) ore (iii) gangue.
(i) Mineral: an element or compound occurring naturally in the earth's crust. (ii) Ore: a mineral from which a metal can be extracted profitably. (iii) Gangue: impurities such as soil and sand mixed with the mined ore.
Page 53, Q2: Name two metals found in nature in the free state.
Gold and silver (also platinum and copper).
Page 53, Q3: What chemical process is used for obtaining a metal from its oxide?
Reduction — e.g. with carbon: ZnO(s) + C(s) → Zn(s) + CO(g).
Activity 3.14 (page 53): What does this tell us about the conditions under which iron rusts?
Iron rusts only when both air (oxygen) and water are present (tube A); without dissolved air (B) or without moisture (C) there is no rust.
Page 54: Galvanised articles are protected even if the zinc coat is broken. Reason it out.
Zinc is more reactive than iron, so zinc reacts (is oxidised) in preference: Zn → Zn2+ + 2e−. The exposed iron is spared.
Page 55, Q1: Oxides of zinc, magnesium and copper heated with the metals zinc, magnesium and copper — where does displacement occur?
Only where the metal is above the oxide's metal: Mg + ZnO → MgO + Zn; Zn + CuO → ZnO + Cu; Mg + CuO → MgO + Cu. No reaction in the other six cases (a metal with its own oxide, or a less reactive metal).
Page 55, Q2: Which metals do not corrode easily?
Gold, platinum and silver (silver tarnishes slowly) — low in the reactivity series. Aluminium and stainless steel resist corrosion through a protective oxide layer.
Page 55, Q3: What are alloys?
Homogeneous mixtures of two or more metals, or of a metal and a non-metal — e.g. steel, brass, bronze, solder.
NCERT exercise — answer outlines
Reading NCERT's Exercises and the ‘Collection of gas’ figure (pages 56–57)Sixteen questions — four multiple-choice, then reasoning and equations. An unnumbered figure for question 9 shows a hand holding a spatula of sulphur powder in a burner flame, with an inverted test tube held over it by tongs to collect the fumes. The point of the figure: the gas collected is sulphur dioxide, a non-metal oxide. NCERT's answers page (page 218) gives 1 (d), 2 (c), 3 (a), 4 (c).
1. Which pair will give a displacement reaction? (a) NaCl solution and copper (b) MgCl₂ solution and aluminium (c) FeSO₄ solution and silver (d) AgNO₃ solution and copper.
(d) — copper is above silver: Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s). In (a)–(c) the metal is below the one in solution (checked from the series in this page's source).
2. Which method is suitable for preventing an iron frying pan from rusting? (a) grease (b) paint (c) a coating of zinc (d) all of the above.
NCERT's answer is (c): grease and paint would burn off or contaminate food when the pan is heated, so of the three, a zinc coat is NCERT's choice. Many guides answer (d) because all three prevent rusting in general — in an NCERT-based test write (c); in a general ‘ways to prevent rusting’ question all three count. (Beyond NCERT: zinc-coated cookware is not recommended for acidic foods.)
3. An element reacts with oxygen to give a compound with a high melting point, also soluble in water. The element is likely to be (a) calcium (b) carbon (c) silicon (d) iron.
(a) Calcium: 2Ca + O2 → 2CaO; CaO is ionic with a very high melting point (2850 K, Table 3.4) and reacts with water: CaO + H2O → Ca(OH)2. Carbon gives a gas; silicon's oxide (sand) and iron's oxide do not dissolve.
4. Food cans are coated with tin and not zinc because (a) zinc is costlier (b) zinc has a higher melting point (c) zinc is more reactive than tin (d) zinc is less reactive than tin.
(c) — zinc is more reactive and would react with acids in food; tin is less reactive than iron and zinc.
5. With a hammer, a battery, a bulb, wires and a switch: (a) how would you distinguish metals from non-metals? (b) Assess the usefulness of these tests.
(a) Hammer: metals flatten (malleable); non-metals shatter (brittle). Circuit: metals light the bulb; non-metals do not. (b) Useful but not conclusive: graphite conducts though a non-metal; sodium is too soft and reactive to test by hammering; iodine is lustrous. Chemical tests (nature of the oxide) are more reliable.
6. What are amphoteric oxides? Give two examples.
Metal oxides that react with both acids and bases to give salt and water. Aluminium oxide: Al2O3 + 6HCl → 2AlCl3 + 3H2O; Al2O3 + 2NaOH → 2NaAlO2 + H2O. Zinc oxide: ZnO + 2HCl → ZnCl2 + H2O; ZnO + 2NaOH → Na2ZnO2 + H2O.
7. Name two metals which will displace hydrogen from dilute acids, and two which will not.
Will: zinc, magnesium (also iron, aluminium) — above hydrogen. Will not: copper, silver (also gold) — below hydrogen.
8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Anode: impure M. Cathode: a thin strip of pure M. Electrolyte: a solution of a soluble salt of M (for copper, acidified copper sulphate).
9. Pratyush heated sulphur and collected the gas. (a) Its action on (i) dry litmus (ii) moist litmus? (b) Balanced equation.
(a) (i) No change on dry litmus (no water, so no acid forms). (ii) Moist blue litmus turns red: SO2 + H2O → H2SO3 (sulphurous acid). (b) S + O2 → SO2.
10. State two ways to prevent the rusting of iron.
Any two: painting, oiling or greasing, galvanising, chrome plating, alloying (stainless steel).
11. What type of oxides are formed when non-metals combine with oxygen?
Acidic oxides (e.g. SO2, CO2); some are neutral (e.g. CO — Beyond NCERT example), as NCERT's summary allows.
12. Give reasons: (a) Pt, Au, Ag are used for jewellery (b) Na, K, Li are stored under oil (c) aluminium, though highly reactive, is used for cooking utensils (d) carbonate and sulphide ores are converted into oxides during extraction.
(a) They are lustrous, malleable, ductile and so unreactive that they do not corrode or tarnish easily. (b) They react vigorously with oxygen and water and can catch fire; oil keeps air and moisture away. (c) A protective oxide layer stops further reaction; aluminium is also light, a good heat conductor and malleable. (d) It is easier to reduce an oxide to the metal than a sulphide or carbonate — hence roasting and calcination.
13. Why do lemon or tamarind juice clean tarnished copper vessels?
The dull coat is basic copper carbonate (and copper oxide); the acids in lemon (citric) and tamarind (tartaric) dissolve it as a soluble copper salt, exposing shiny copper: CuCO3·Cu(OH)2 + 4H+ → 2Cu2+ + CO2 + 3H2O; CuO + 2H+ → Cu2+ + H2O (ionic equations Beyond NCERT).
14. Differentiate between metals and non-metals on the basis of chemical properties.
Metals: form basic oxides (Al2O3, ZnO amphoteric); lose electrons to form cations; those above H displace hydrogen from dilute acids; form ionic chlorides. Non-metals: form acidic or neutral oxides; gain electrons to form anions; do not displace hydrogen from dilute acids; react with hydrogen to form hydrides (NCERT summary, page 56; chlorides covalent — Beyond NCERT).
15. A fake goldsmith dipped gold bangles in a solution; they sparkled but lost much weight. What was the solution?
Aqua regia — concentrated HCl and HNO3 in 3 : 1. It dissolves gold; the outer layer was dissolved away (exposing a fresh shiny surface) and the dissolved gold went with the ‘goldsmith’.
16. Why is copper used to make hot-water tanks and not steel?
Copper does not react with water or steam (NCERT page 43) and is an excellent conductor of heat; steel, mostly iron, reacts with steam and rusts in hot water and air.
What to remember
Numbers
Gold wireabout 2 km from 1 g of gold (most ductile metal)
Aqua regiaconcentrated HCl : HNO₃ = 3 : 1, freshly prepared
Reactivity series (13)K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au
Activity 3.11 orderMg > Al > Zn > Fe; Cu no reaction with dilute HCl
Activity 3.12record after 20 minutes
Sodium / chlorineNa 2,8,1 → Na⁺ 2,8 · Cl 2,8,7 → Cl⁻ 2,8,8 (17 protons, 18 electrons)
Table 3.4 (K)NaCl 1074/1686 · LiCl 887/1600 · CaCl₂ 1045/1900 · CaO 2850/3120 · MgCl₂ 981/1685
Steel (NCERT)iron + about 0.05% carbon
22-carat gold22 parts gold + 2 parts Cu or Ag (≈ 91.67% gold); 24 carat = pure
Delhi iron pillarmore than 1600 years old · 8 m high · 6 tonnes (6000 kg)
Activity 3.14about 1 mL oil over boiled distilled water in tube B
Iron + steam3Fe + 4H₂O → Fe₃O₄ + 4H₂
Chapter sizepages 37–57 · 14 activities · Figures 3.1–3.13 · Tables 3.1–3.4 · 16 exercises
One-liners
- Metals: lustrous, malleable, ductile, sonorous, good conductors; mercury is the only liquid metal, bromine the only liquid non-metal.
- Iodine is a lustrous non-metal; graphite conducts; diamond is the hardest natural substance.
- Metal oxides are basic; Al2O3 and ZnO are amphoteric; non-metal oxides are acidic or neutral.
- Na and K are kept under kerosene; Mg, Al, Zn, Pb carry protective oxide layers; Ag and Au do not react with oxygen.
- K, Na: violent with cold water · Ca: gentle · Mg: hot water · Al, Fe, Zn: steam · Pb, Cu, Ag, Au: none.
- Nitric acid gives no hydrogen (oxidising) — except Mg and Mn with very dilute acid.
- A metal displaces any metal below it in the series from its salt solution.
- Ionic compounds: transfer of electrons; hard, brittle, high-melting, water-soluble, conduct when molten or dissolved.
- Roasting: sulphide, excess air · calcination: carbonate, limited air · then reduce the oxide.
- Thermit: Fe2O3 + 2Al → 2Fe + Al2O3 — joins railway tracks.
- Electrolytic refining: impure anode, pure cathode, metal-salt electrolyte, anode mud.
- Rusting needs air and water; galvanising (zinc) protects even when scratched.
- Brass = Cu + Zn · bronze = Cu + Sn · solder = Pb + Sn · stainless steel = Fe + Ni + Cr · amalgam contains Hg.
Traps to avoid
- Brass is copper + zinc; bronze is copper + tin — not the reverse.
- Roasting needs excess air (sulphide ores); calcination needs limited air (carbonate ores).
- In refining the impure metal is the anode; in extraction by electrolysis the metal collects at the cathode.
- Sodium is kept in kerosene because it reacts with air and moisture — not because it melts in air.
- Solid ionic compounds do not conduct; molten or dissolved ones do.
- Aqua regia is 3 HCl : 1 HNO3; neither acid alone dissolves gold.
- Food cans: tin, not zinc — zinc is more reactive. Galvanised iron: zinc protects even when scratched; tin does not.
- Iron + steam gives Fe3O4, not Fe2O3.
- 18 carat = 18 parts gold + 6 parts other metals (75%), not 18% gold.
- NCERT slips: Figure 3.9 puts Cu with carbon reduction while the text gets Cu by heating alone; ‘C1–’ for Cl−; solder ‘welding’ for soldering; the summary's non-metal hydrides are not taught in the body.
How to strategise
Prelims — what UPSC asks
- Corrosion and galvanising are UPSC's favourite part: galvanising = zinc coating (1982, 1992, 1994); galvanised pipes resist rust because zinc oxidises more readily than iron (1983); rusting increases weight (1980); anodising deposits aluminium oxide (2000).
- Alloys: stainless steel (1980), ‘which is not an alloy’ — zinc (1984, 1989), 18-carat gold (2004), solder = lead + tin (2006). Learn composition and the reason each alloy is used.
- Reactivity and extraction: sodium under kerosene, with ‘melts in air’ as a false reason (1998); coke as reducing agent and fuel in the blast furnace (1998). Ionic compounds: solids do not conduct (2003). Heat conduction: copper feels hotter than glass (2001).
- Likely next: amphoteric oxides, aqua regia, the thermit reaction, roasting vs calcination, anode mud, nitric acid and hydrogen, the iron pillar, liquid and low-melting metals. Ore names (bauxite, haematite, galena) come from the geography chapters.
- Answer-key note (2001, copper vs glass): the stored key is (c) ‘A is true but R is false’. The assertion is true — copper conducts heat far better, so it delivers heat to the skin faster. But the reason, ‘the density of copper is more than that of glass’, is also true (copper about 8.9 g/cm³, glass about 2.5 g/cm³); it simply does not explain the assertion. The correct option is (b) both true, R not the correct explanation; treat the stored key as likely wrong.
- Answer-key note (2003, ionic compounds): statement 2 is plainly false (solid ionic compounds do not conduct). Statement 1, ‘insoluble in alcohol’, is a textbook generalisation — NCERT itself says kerosene and petrol — and some ionic salts do dissolve in alcohol. The stored key (a) ‘only 1’ stands as the best available option; treat the question as slightly flawed rather than the key as wrong.
Mains — where it appears and how to answer
- No GS Mains question in the bank so far is built on this chapter's core content. It supplies the science for GS3 answers on mining and metallurgy pollution (sulphur dioxide from roasting sulphide ores, heavy metals in slag — Beyond NCERT), corrosion and infrastructure maintenance, metal recycling and critical minerals, and for GS1 notes on India's metallurgical heritage (the Delhi iron pillar).
- Answer frame: process (one balanced equation or a reactivity-series line) → why it matters (economy, safety, environment) → prevention or control (coatings, alloys, emission scrubbing, recycling) → a line on policy, attributed.
- A small sketch — the reactivity ladder with extraction bands, or the galvanised-vs-tin-plate panel — fits in a 150-word answer.
Self-check
Tap an option. NCERT's own exercise questions come first; the rest test the figures and common confusions.
1. Which non-metal is a good conductor of electricity?
2. Which pair consists of amphoteric oxides?
3. An iron nail is placed in copper sulphate solution. What is seen after 20 minutes?
4. Which statement about ionic compounds is correct?
5. Heating a carbonate ore strongly in limited air to convert it into the oxide is called:
6. In the electrolytic refining of copper, the anode is:
7. Galvanised iron stays protected even when the coating is scratched because:
8. Bronze is an alloy of:
UPSC questions from this chapter
Open any question to attempt it in the Question bank — your attempt is saved to your progress.