BharatNotes Why this chapter matters for UPSC: This is Chapter 3 of NCERT's Class X Science (Reprint 2026-27). It ranks metals by how readily they react, and then uses that one ranking to explain three things: which metals are found free in nature, which must be won from their ores by carbon and which by electricity, and why iron rusts while gold keeps its shine. Prelims general science draws on all of it (amphoteric oxides, aqua regia, galvanising, anodising, carats, the thermit reaction), and the idea of an ore sits under every GS3 question on minerals.
Contemporary hook: The US Geological Survey's Mineral Commodity Summaries 2026 records that in April 2025 "China tightened its export controls on rare-earth elements", expanded them in October, and in November "suspended the October export controls for 1 year". Rare earths are metals too. Whether a country can supply them turns first on this chapter's distinction between a mineral and an ore.
🧠 First Principles — Read This First
Properties sort elements, but only roughly. Metals are lustrous, malleable, ductile, sonorous and good conductors; non-metals are mostly the opposite. NCERT's own list of exceptions shows why "we cannot group elements according to their physical properties alone": mercury is a liquid metal, gallium and caesium melt on the palm, iodine is a lustrous non-metal, graphite conducts electricity, and diamond is the hardest natural substance known.
Chemistry sorts them more clearly. Metals form basic oxides and give up electrons to become positive ions; non-metals form acidic or neutral oxides and take electrons to become negative ions. NCERT explains both through the noble gases: "We, therefore, explain the reactivity of elements as a tendency to attain a completely filled valence shell." Sodium loses one electron, chlorine gains one, and the ions they form hold together as sodium chloride.
One ranking runs the chapter. The reactivity series (K, Na, Ca, Mg, Al, Zn, Fe, Pb, [H], Cu, Hg, Ag, Au) is built from displacement: if metal A displaces metal B from its salt solution, A is the more reactive. The same order predicts which metals react with cold water, which free hydrogen from dilute acids, which are found free in nature, and which method extracts each one.
Extraction is reduction; corrosion undoes it. "Obtaining metals from their compounds is also a reduction process." Left in moist air, metals drift back towards compounds: silver gets a black coat of silver sulphide, copper a green coat of basic copper carbonate, iron brown flaky rust. Painting, galvanising, anodising and alloying all work by keeping air and water away or by changing the metal.
PART 1 — Quick Reference
Table 1: Physical properties, and NCERT's exceptions
| Property | NCERT's statement | Exception NCERT gives |
|---|---|---|
| State | All metals are solid at room temperature | Mercury is a liquid; gallium and caesium "have very low melting points" and "will melt if you keep them on your palm" |
| Lustre | Metals in their pure state have a shining surface (metallic lustre) | Iodine is a non-metal but lustrous |
| Malleability and ductility | Gold and silver are the most malleable metals; "Gold is the most ductile metal": about 2 km of wire from one gram | Non-metals are neither malleable nor ductile |
| Hardness | Metals are generally hard, and hardness varies | Lithium, sodium and potassium are soft enough to cut with a knife, with low densities and low melting points; diamond, a non-metal, is the hardest natural substance |
| Heat conduction | Metals conduct heat and have high melting points; best conductors silver and copper | Lead and mercury are comparatively poor conductors of heat |
| Electrical conduction | Metals conduct electricity (Activity 3.6) | Graphite, a non-metal, conducts electricity |
| Physical state of non-metals | Solids or gases | Bromine is a liquid non-metal |
Source: NCERT, Science Class X, ch. 3, Reprint 2026-27, section 3.1 and Activities 3.1-3.7 (pp. 37-40); summary (pp. 55-56).
Table 2: How metals react
| With | What happens | NCERT's examples |
|---|---|---|
| Oxygen | Metal + oxygen → metal oxide, usually basic | 2Cu + O₂ → 2CuO (black); 4Al + 3O₂ → 2Al₂O₃; Na₂O + H₂O → 2NaOH and K₂O + H₂O → 2KOH (alkalis) |
| Oxygen, by reactivity | K and Na catch fire in the open, so are kept in kerosene; Mg, Al, Zn, Pb carry a protective oxide layer; iron filings burn in a flame; copper gets a black CuO coat; silver and gold do not react even at high temperatures | Magnesium burns with a dazzling white flame (Activity 3.8) |
| Cold water | K and Na react violently, and the hydrogen catches fire; Ca reacts less violently and floats | 2Na + 2H₂O → 2NaOH + H₂ + heat; Ca + 2H₂O → Ca(OH)₂ + H₂ |
| Hot water | Mg reacts, gives magnesium hydroxide and hydrogen, and floats | Mg + 2H₂O → Mg(OH)₂ + H₂ (NCERT gives this in words) |
| Steam | Al, Fe and Zn react with neither cold nor hot water, but do react with steam, giving the oxide and hydrogen | 2Al + 3H₂O(g) → Al₂O₃ + 3H₂; 3Fe + 4H₂O(g) → Fe₃O₄ + 4H₂ |
| No reaction with water | Lead, copper, silver and gold | |
| Dilute HCl | Salt + hydrogen; fastest and hottest with Mg; order Mg > Al > Zn > Fe; copper does not react | Mg + 2HCl → MgCl₂ + H₂; 2Al + 6HCl → 2AlCl₃ + 3H₂; Zn + 2HCl → ZnCl₂ + H₂; Fe + 2HCl → FeCl₂ + H₂ (NCERT asks students to write these; balanced here) |
| Nitric acid | Usually no hydrogen: HNO₃ oxidises it to water and is itself reduced to N₂O, NO or NO₂; Mg and Mn give H₂ with very dilute HNO₃ | |
| Salt solution of another metal | A more reactive metal displaces a less reactive one | Fe + CuSO₄ → FeSO₄ + Cu (Activity 3.12; copper wire in iron sulphate shows no change) |
Source: NCERT, Science Class X, ch. 3, Reprint 2026-27, sections 3.2.1-3.2.4 and Activities 3.8-3.12 (pp. 40-45).
Table 3: The reactivity series and how each metal is won
| Metals (Table 3.2 order) | Where NCERT places them | Found in nature as | Extraction |
|---|---|---|---|
| K, Na, Ca, Mg, Al | Top: "so reactive that they are never found in nature as free elements" | Compounds only | Electrolytic reduction: Na, Mg and Ca from their molten chlorides; Al from aluminium oxide. Carbon cannot reduce their oxides |
| Zn, Fe, Pb (and copper, see Table 6) | Middle: moderately reactive | Mainly oxides, sulphides or carbonates | Sulphide ores roasted, carbonate ores calcined, to oxides; oxide then reduced by carbon (ZnO + C → Zn + CO) or by a more reactive metal |
| [H] | Hydrogen is placed between Pb and Cu | Metals above it displace hydrogen from dilute acids | |
| Cu, Hg | Low reactivity | Cu also free; Hg as cinnabar (HgS); Cu as Cu₂S | Heating alone: 2HgS + 3O₂ → 2HgO + 2SO₂, then 2HgO → 2Hg + O₂; 2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂, then 2Cu₂O + Cu₂S → 6Cu + SO₂ |
| Ag, Au | Least reactive | Often free (with platinum and copper); Ag also as sulphide or oxide ores |
After extraction, many metals (copper, zinc, tin, nickel, silver, gold) are purified by electrolytic refining.
Source: NCERT, Science Class X, ch. 3, Reprint 2026-27, Table 3.2 (p. 45), sections 3.4.1-3.4.6 (pp. 49-53).
Table 4: Ionic compounds
| Ionic compound | Melting point (K) | Boiling point (K) |
|---|---|---|
| NaCl | 1074 | 1686 |
| LiCl | 887 | 1600 |
| CaCl₂ | 1045 | 1900 |
| CaO | 2850 | 3120 |
| MgCl₂ | 981 | 1685 |
Properties: solid and somewhat hard but brittle; high melting and boiling points; generally soluble in water and insoluble in kerosene and petrol; conduct electricity in solution and when molten, but not as solids.
Source: NCERT, Science Class X, ch. 3, Reprint 2026-27, Table 3.4 (p. 48) and section 3.3.1 (pp. 48-49).
Table 5: Corrosion, its prevention, and alloys
| Item | NCERT's statement |
|---|---|
| Silver | Turns black: reacts with sulphur in the air to form silver sulphide |
| Copper | Loses its shiny brown surface and gains a green coat of basic copper carbonate (moist carbon dioxide in air) |
| Iron | Brown flaky rust; Activity 3.14 shows nails rust only when both air and water are present |
| Prevention | Painting, oiling, greasing, galvanising, chrome plating, anodising, making alloys |
| Galvanisation | A thin layer of zinc on steel or iron; protects "even if the zinc coating is broken" |
| Anodising | Aluminium article made the anode in dilute sulphuric acid; the oxygen released thickens the oxide layer, which can be dyed |
| Steel | Iron with a small amount of carbon (about 0.05 %) becomes hard and strong; with nickel and chromium it becomes stainless steel |
| Gold | 24 carat is pure and very soft; 22 carat = 22 parts gold with 2 parts copper or silver |
| Amalgam | An alloy in which one of the metals is mercury |
| Brass, bronze, solder | Brass = Cu + Zn; bronze = Cu + Sn (both poorer conductors than copper); solder = Pb + Sn, low melting point |
Source: NCERT, Science Class X, ch. 3, Reprint 2026-27, section 3.5 and Activity 3.14 (pp. 53-54); anodising box (p. 42).
Table 6: NCERT lines to read with care
| NCERT says | The record |
|---|---|
| Copper is in three places: "gold, silver, platinum and copper are found in the free state" (p. 50); copper from Cu₂S "by just heating in air", under metals low in the series (p. 51); and "The metals in the middle of the activity series such as iron, zinc, lead, copper, are moderately reactive" (p. 51) | Not a contradiction to fear in an exam, but read it as one metal with several ores. In Table 3.2 copper sits just below hydrogen, which is why it does not react with dilute HCl. |
| Exercise 2, iron frying pan: options grease, paint, zinc coating, "All of the above" | NCERT's printed answer is (c), a coating of zinc (Answers, p. 218), although section 3.5.1 also lists painting and greasing as ways to prevent rusting. |
| Exercise 4, food cans coated with tin and not zinc | NCERT's answer is (c), "zinc is more reactive than tin". Tin is not in NCERT's Table 3.2, so this answer needs the fact itself, not the table. |
Source: NCERT, Science Class X, Reprint 2026-27, ch. 3 pp. 45, 50-51, 54, 56; Answers (p. 218).
PART 2 — Concepts & Narrative
Physical properties (3.1)
NCERT starts with samples of iron, copper, aluminium, magnesium, sodium, lead and zinc. Rubbed with sandpaper, metals show metallic lustre. Struck with a hammer, many flatten into sheets (malleability; gold and silver are the most malleable). Drawn into wires, they show ductility: "Gold is the most ductile metal. You will be surprised to know that a wire of about 2 km length can be drawn from one gram of gold." Activity 3.5 (a pin waxed to a heated wire) shows that metals conduct heat and have high melting points: "The best conductors of heat are silver and copper. Lead and mercury are comparatively poor conductors of heat." Metals ring when struck (sonorous), which is why school bells are metal, and they conduct electricity, which is why household wires carry a coat of PVC or a rubber-like material.
Non-metals (carbon, sulphur, iodine, oxygen, hydrogen) are few. They are solids or gases, "except bromine which is a liquid". Activity 3.7 runs Activities 3.1 to 3.4 and 3.6 on carbon, sulphur and iodine, which completes NCERT's Table 3.1 and leads to the main lesson: the exceptions (Table 1 above) are too many to sort elements by physical properties alone.
Allotrope: one of the different forms in which an element exists. Diamond and graphite are both carbon. Diamond is the hardest natural substance known and has very high melting and boiling points; graphite conducts electricity.
Metals and oxygen (3.2.1)
"Almost all metals combine with oxygen to form metal oxides." Copper heated in air gives black copper(II) oxide; aluminium gives aluminium oxide. Metal oxides are generally basic: recall from Chapter 2 that copper oxide dissolves in hydrochloric acid to give a salt and water. Two oxides break the rule.
Amphoteric oxide: NCERT's term for "metal oxides which react with both acids as well as bases to produce salts and water". NCERT's examples are aluminium oxide and zinc oxide: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O Al₂O₃ + 2NaOH → 2NaAlO₂ (sodium aluminate) + H₂O The term is for the oxide. "Amphoteric metal" is not NCERT's phrase.
Most metal oxides do not dissolve in water, but sodium oxide and potassium oxide dissolve to form the alkalis NaOH and KOH. Burning magnesium (Activity 3.8) gives an ash whose solution turns red litmus blue (2Mg + O₂ → 2MgO; MgO + H₂O → Mg(OH)₂), while burning sulphur gives a gas whose solution turns blue litmus red (S + O₂ → SO₂). That pair is the quickest chemical test of metal against non-metal.
Metals do not react with oxygen at the same rate. Potassium and sodium "react so vigorously that they catch fire if kept in the open", so "they are kept immersed in kerosene oil". Magnesium, aluminium, zinc and lead are covered by a thin oxide layer at ordinary temperature, and "The protective oxide layer prevents the metal from further oxidation." Iron does not burn on heating, but iron filings sprinkled into a flame burn vigorously. Copper does not burn, though hot copper turns black with copper(II) oxide. "Silver and gold do not react with oxygen even at high temperatures."
Anodising: making the oxide layer thicker on purpose. Aluminium in air develops a thin oxide layer that resists further corrosion. In anodising, 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 a thicker protective layer, which can also be dyed. That is why Exercise 12(c) has an answer: aluminium is highly reactive, yet its oxide coat makes it usable for cooking utensils.
Metals and water (3.2.2)
Metals that react with water give a metal oxide and hydrogen; a soluble oxide then forms the hydroxide. The reactions fall into steps:
- Cold water, violently: potassium and sodium. "In case of sodium and potassium, the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire."
- Cold water, less violently: calcium. The heat is not enough to ignite the hydrogen, and "Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal."
- Hot water only: magnesium. "Magnesium does not react with cold water." In hot water it forms magnesium hydroxide and hydrogen, and it too floats on its bubbles.
- Steam only: aluminium, iron and zinc, giving the oxide and hydrogen (iron gives Fe₃O₄).
- Not at all: "Metals such as lead, copper, silver and gold do not react with water at all."
This step order is the reactivity series seen through water. It also answers Exercise 16: copper does not react with water, while iron (the main metal in steel) reacts with steam, so copper suits hot-water tanks.
Metals and acids (3.2.3)
With dilute hydrochloric acid, metals give a salt and hydrogen. In Activity 3.11 bubbles form fastest with magnesium, which also gives the highest temperature, and "The reactivity decreases in the order Mg > Al > Zn > Fe." Copper gives no bubbles and no temperature change: it does not react with dilute HCl.
Nitric acid is the exception. "It is because HNO3 is a strong oxidising agent." It oxidises the hydrogen to water and is reduced to an oxide of nitrogen (N₂O, NO or NO₂), so hydrogen is not evolved. Only magnesium and manganese give hydrogen, and only with very dilute nitric acid.
Aqua regia ("royal water"). A freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1. It dissolves gold, although neither acid can do so alone, and NCERT calls it "one of the few reagents that is able to dissolve gold and platinum". It is highly corrosive and fuming. Exercise 15's travelling "goldsmith" who returned bright but much lighter bangles had dipped them in such a solution.
Metals and salt solutions, and the reactivity series (3.2.4-3.2.5)
Oxygen, water and acids cannot rank every metal, because some metals react with none of them. Displacement can. An iron nail in copper sulphate solution gets a coat of copper, while a copper wire in iron sulphate solution stays unchanged (Activity 3.12). NCERT's rule: "if metal A displaces metal B from its solution, it is more reactive than B." From displacement experiments (Activities 1.9 and 3.12) comes Table 3.2, the activity series, from potassium (most reactive) to gold (least).
Hydrogen sits in the series, in brackets, between lead and copper. "Metals above hydrogen in the Activity series can displace hydrogen from dilute acids." So zinc and magnesium free hydrogen from dilute acid, copper and silver do not (Exercise 7). The series also settles Exercise 1: only copper in silver nitrate solution reacts, because sodium, magnesium and iron each sit above the metal offered to replace them.
How metals and non-metals react (3.3)
Noble gases, with a full outer shell, hardly react. Other atoms react to reach that state. Sodium (2, 8, 1) loses its single outer electron and becomes the cation Na⁺ (2, 8); chlorine (2, 8, 7) takes it and becomes the anion Cl⁻ (2, 8, 8). The oppositely charged ions are held by strong electrostatic forces. NCERT adds a point often missed: "sodium chloride does not exist as molecules but aggregates of oppositely charged ions." Magnesium (2, 8, 2) gives one electron to each of two chlorine atoms to form MgCl₂, with Mg²⁺ and two Cl⁻ ions. Compounds formed by such transfer of electrons from a metal to a non-metal are "ionic compounds or electrovalent compounds".
Why ionic compounds behave as they do (3.3.1). Strong attraction between ions makes them hard but brittle solids with high melting and boiling points (Table 4). They generally dissolve in water but not in kerosene or petrol. "Ionic compounds in the solid state do not conduct electricity because movement of ions in the solid is not possible due to their rigid structure." Melted or dissolved, the ions move and carry current.
Occurrence and extraction of metals (3.4)
The earth's crust is the main source of metals, and seawater holds soluble salts such as sodium and magnesium chlorides. Two words are easy to confuse. Naturally occurring elements or compounds are minerals; minerals from which a metal "can be profitably extracted" are ores. Many ores are oxides, "because oxygen is a very reactive element and is very abundant on the earth."
Where a metal sits in the series decides how it is found and won (Table 3). Ores are first freed of gangue (soil, sand and other impurities), using differences in the physical or chemical properties of gangue and ore.
- Low in the series: heating alone reduces the oxide. Cinnabar (HgS) is roasted to mercuric oxide, which further heating turns to mercury; Cu₂S gives copper the same way.
- Middle of the series: first make an oxide, "easier to obtain a metal from its oxide". Sulphide ores are roasted (heated strongly in excess air: 2ZnS + 3O₂ → 2ZnO + 2SO₂); carbonate ores are calcined (heated strongly in limited air: ZnCO₃ → ZnO + CO₂). The oxide is then reduced by carbon (ZnO + C → Zn + CO) or by a more reactive metal.
- Top of the series: "carbon cannot reduce the oxides of sodium, magnesium, calcium, aluminium" because "these metals have more affinity for oxygen than carbon". They are won by electrolysis: sodium, magnesium and calcium from their molten chlorides (metal at the cathode, Na⁺ + e⁻ → Na; chlorine at the anode, 2Cl⁻ → Cl₂ + 2e⁻), aluminium from aluminium oxide.
The thermit reaction. Reducing a metal oxide with a more reactive metal releases so much heat that the metal comes out molten. With manganese dioxide: 3MnO₂ + 4Al → 3Mn(l) + 2Al₂O₃ + heat. With iron(III) oxide: Fe₂O₃ + 2Al → 2Fe(l) + Al₂O₃ + heat. "This reaction is known as the thermit reaction", and NCERT names its uses: joining railway tracks and cracked machine parts. In both equations aluminium is oxidised and the other metal's oxide is reduced.
Refining (3.4.6). Metals from these processes are impure, and "The most widely used method for refining impure metals is electrolytic refining." Copper, zinc, tin, nickel, silver and gold are refined this way. The impure metal is the anode, a thin strip of pure metal the cathode, and a solution of the metal's salt the electrolyte (acidified copper sulphate for copper). Pure metal dissolves from the anode and an equal amount deposits on the cathode; soluble impurities stay in solution and insoluble ones settle below the anode as anode mud. This is the full answer to Exercise 8.
Corrosion and its prevention (3.5)
NCERT recalls three cases from Chapter 1: silver turns black (silver sulphide), copper turns green (basic copper carbonate) and iron rusts. Activity 3.14 isolates the cause. Nails in tube A (water and air) rust; nails in tube B (boiled water under a layer of oil, so no dissolved air) and tube C (dry air over anhydrous calcium chloride) do not. Iron needs both air and water to rust.
Rusting is prevented by painting, oiling, greasing, galvanising, chrome plating, anodising or making alloys. In galvanisation, steel and iron get a thin coat of zinc, and the article "is protected against rusting even if the zinc coating is broken." NCERT leaves the reason as a question; the reactivity series points to it, since zinc stands above iron.
Alloys. 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 main metal and dissolving the others in it in definite proportions. NCERT notes that an alloy's electrical conductivity and melting point are lower than those of the pure metals: brass (copper and zinc) and bronze (copper and tin) are poor conductors next to copper, and solder (lead and tin) melts low enough to join electrical wires. "If one of the metals is mercury, then the alloy is known as an amalgam."
Carat: the share of gold in 24 parts. Pure gold, 24 carat, is very soft and unsuitable for jewellery, so it is alloyed with silver or copper. In India, 22 carat gold is generally used for ornaments: "22 parts of pure gold is alloyed with 2 parts of either copper or silver."
The iron pillar at Delhi. NCERT's "More to Know!" box calls it "The wonder of ancient Indian metallurgy". The pillar near the Qutub Minar was "built more than 1600 years ago by the iron workers of India", who "had developed a process which prevented iron from rusting", and scientists from all parts of the world have examined it. NCERT gives its height as 8 m and its weight as 6 tonnes (6000 kg).
Did the 2020-21 edition differ?
No. This chapter's sections, activities, boxes and exercises read the same in the 2020-21 edition and in Reprint 2026-27.
Source: NCERT, Science Class X, 2020-21 edition (whole-book zip, Wayback Machine capture of 9 October 2021), compared with Reprint 2026-27.
Beyond the textbook: rare earths and critical minerals
What the rare earths are. The Indian Bureau of Mines defines them precisely: "The Rare-Earth Elements (REEs) are a group of 17 elements, namely, yttrium (Y), scandium (Sc) and lanthanides (15 elements in the periodic table with atomic numbers 57 to 71". It divides them into light REE (lanthanum to europium) and heavy REE (gadolinium to lutetium), with yttrium and scandium "clubbed with HREE". The usual slip is to call all seventeen lanthanides.
Mineral, ore, reserve. NCERT's line between a mineral and an ore is exactly the line between rare earths in the crust and rare earths that can be mined. USGS puts it this way: "Rare earths are relatively abundant in the Earth’s crust, but minable concentrations are less common than for most other mineral commodities." Its Mineral Commodity Summaries 2026 lists reserves (tonnes of rare-earth-oxide equivalent) of 44 million for China, 11 million for Brazil and 6.3 million for Australia, and a world total above 75 million. For India it prints no reserve figure ("NA"), with the note: "A 2015 report from OSCOM indicated that monazite reserves from their operations were 256,000 tons; rare-earth reserves were not reported." Mine production tells the supply story: India 2,900 tonnes in 2024 and 2025 (estimated), China 270,000 tonnes, world 390,000 tonnes in 2025 (estimated). Older lines that rank India's reserves third come from earlier editions and are not supported by the 2026 one.
India's list and mission. The Ministry of Mines told the Rajya Sabha on 24 July 2023 that "Government has released a list of 30 critical minerals for India"; the list includes copper and tin (two of NCERT's electrolytically refined metals), nickel, cobalt, lithium, graphite and REE. On 29 January 2025 the Union Cabinet approved the National Critical Mineral Mission "with an expenditure of Rs.16,300 crore and expected investment of Rs.18,000 crore by PSUs, etc.", an outlay of Rs 34,300 crore over seven years. It covers "mineral exploration, mining, beneficiation, processing, and recovery from end-of-life products", the same chain this chapter teaches as ore, enrichment, extraction and refining, plus recycling.
Source: Indian Bureau of Mines, Indian Minerals Yearbook 2024 (63rd edition), rare earths; USGS, Mineral Commodity Summaries 2026, "Rare Earths"; PIB (Ministry of Mines), 24 July 2023, Release ID 1942027; PIB (Cabinet), 29 January 2025, Release ID 2097308.
PART 3 — UPSC Integration
Cross-paper relevance
- Prelims (general science) — exceptions to metal and non-metal properties, amphoteric oxides, reactions with water and steam, nitric acid and hydrogen, aqua regia, the reactivity series, roasting versus calcination, the thermit reaction, galvanising and anodising, carats, amalgam, brass and bronze.
- GS3 (Science and technology) — extraction and electrolytic refining; corrosion and its prevention; alloys.
- GS3 (Economy) — critical minerals, rare earths and the National Critical Mineral Mission; why reserves and mine output are different measures.
- GS1 (Indian heritage) — the rust-resistant iron pillar at Delhi as ancient Indian metallurgy.
Past questions on these themes: Prelims 2026 (rare-earth elements and the National Critical Mineral Mission; question ID in the Revision Capsule).
Frames for Mains Answers
1. Reactivity sets the method and the cost. Metals at the bottom of the series are found free or won by heating; those in the middle need roasting or calcination and then carbon; those at the top need electrolysis because they hold oxygen more firmly than carbon does. Use this to explain why aluminium needs electric power while iron needs coke.
2. Corrosion as a maintenance problem. Rust needs air and water (Activity 3.14). Prevention either seals the surface (paint, oil, grease, chrome) or sacrifices a more reactive metal (zinc in galvanising) or changes the metal (stainless steel). The Delhi iron pillar shows the problem is old and was once solved by Indian iron workers.
3. Critical minerals. Begin with mineral versus ore, then reserves versus production: in USGS's 2026 tables China holds the largest rare-earth reserves and mines about 270,000 of 390,000 tonnes, while India mines 2,900 tonnes and has no reported reserve figure. The National Critical Mineral Mission (January 2025, Rs 34,300 crore over seven years) spans exploration to recycling. Date every figure you use.
Exam Strategy
Prelims fact-traps:
- Gold is the most ductile metal; gold and silver are the most malleable. Silver and copper are the best conductors of heat; lead and mercury are poor ones.
- Mercury is the only liquid metal; gallium and caesium melt on the palm. Bromine is the liquid non-metal.
- Iodine is lustrous; graphite conducts; diamond is the hardest natural substance.
- Aluminium oxide and zinc oxide are amphoteric. Sodium and potassium oxides dissolve to form alkalis.
- Sodium and potassium are stored in kerosene. Magnesium needs hot water; aluminium, iron and zinc need steam; lead, copper, silver and gold do not react with water.
- Nitric acid usually gives no hydrogen; only Mg and Mn do, with very dilute HNO₃.
- Aqua regia = concentrated HCl : concentrated HNO₃ = 3 : 1; it dissolves gold and platinum.
- Roasting: sulphide ore, excess air. Calcination: carbonate ore, limited air.
- Thermit: Fe₂O₃ + 2Al; joins railway tracks.
- Electrolytic refining: impure metal at the anode, pure metal deposits on the cathode, anode mud below the anode.
- Galvanising = zinc coat; anodising = thicker oxide layer on aluminium.
- 22 carat = 22 parts gold in 24. Amalgam contains mercury. Brass Cu + Zn; bronze Cu + Sn; solder Pb + Sn.
- Rare earths are 17 elements: scandium, yttrium and the 15 lanthanides.
Mains: NCERT's reactivity series is the explanation layer for any minerals or materials answer; add dated figures only from a named source.
Practice Questions
Questions 1-4 are the NCERT exercise MCQs. Practice (UPSC-pattern, not past papers): questions 5-9.
1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and silver metal
(d) AgNO₃ solution and copper metal.
Answer: (d). Copper is above silver in the activity series; in (a), (b) and (c) the free metal is below the metal in the salt.
2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above.
Answer: (c), as printed in NCERT's answer key. Section 3.5.1 also lists painting and greasing among the ways to prevent rusting.
3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
(a) calcium
(b) carbon
(c) silicon
(d) iron.
Answer: (a). Calcium oxide melts at 2850 K (Table 3.4) and reacts with water to give calcium hydroxide.
4. Food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.
Answer: (c), per NCERT's answer key.
5. With reference to the reactions of metals, consider the following statements:
1. Magnesium reacts with cold water to release hydrogen.
2. Aluminium oxide reacts with both hydrochloric acid and sodium hydroxide.
3. Hydrogen is generally not evolved when a metal reacts with nitric acid.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (b). Magnesium does not react with cold water; it reacts with hot water.
6. Consider the following pairs:
1. Roasting — sulphide ore heated strongly in excess air
2. Calcination — carbonate ore heated strongly in limited air
3. Thermit reaction — iron(III) oxide reduced by carbon
How many of the pairs given above are correctly matched?
(a) Only one
(b) Only two
(c) All three
(d) None
Answer: (b). In the thermit reaction iron(III) oxide is reduced by aluminium.
7. With reference to rare earths and critical minerals, consider the following statements:
1. The rare-earth elements are seventeen: scandium, yttrium and the fifteen lanthanides.
2. The USGS Mineral Commodity Summaries 2026 ranks India third in rare-earth reserves.
3. The National Critical Mineral Mission approved in January 2025 combines government expenditure of Rs 16,300 crore with expected investment of Rs 18,000 crore by PSUs and others.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c). The 2026 edition gives no reserve figure for India.
8. Consider the following statements:
1. Silver articles turn black because silver reacts with sulphur in the air.
2. A galvanised iron article remains protected even if its zinc coating is broken.
3. In anodising, the aluminium article is made the cathode.
Which of the statements given above are correct?
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3
Answer: (b). In anodising the aluminium article is the anode.
9. Why are gold and platinum found free in nature while sodium and aluminium are won only by electrolysis? Explain with the reactivity series, and say why mine production, not reserves alone, decides who supplies rare earths. (150 words)
NCERT exercises (where the answers are on this page): 5 Table 1 and its exceptions; 14 Table 2 and "Metals and oxygen"; 6 the amphoteric-oxide box; 7 "Metals and salt solutions"; 8 "Refining"; 9 S + O₂ → SO₂, which turns moist blue litmus red and leaves dry litmus unchanged; 10 Table 5; 11 acidic or neutral oxides (summary); 12 (a) "Silver and gold do not react with oxygen even at high temperatures", (b) Table 2, (c) the anodising box, (d) "Occurrence and extraction"; 13 the acids in lemon and tamarind react with the green basic copper carbonate (Chapter 2: acid + carbonate); 15 the aqua regia box; 16 "Metals and water".
📦 Revision Capsule
Hard Facts
- Activity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au.
- Amphoteric oxides: Al₂O₃ and ZnO. Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O.
- 2Na + 2H₂O → 2NaOH + H₂ (H₂ catches fire); 3Fe + 4H₂O(g) → Fe₃O₄ + 4H₂.
- Reactivity with dilute HCl: Mg > Al > Zn > Fe; Cu does not react.
- Roasting 2ZnS + 3O₂ → 2ZnO + 2SO₂; calcination ZnCO₃ → ZnO + CO₂; ZnO + C → Zn + CO.
- Cinnabar HgS → HgO → Hg by heating; 2Cu₂O + Cu₂S → 6Cu + SO₂.
- Thermit: Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat.
- Electrolysis of molten NaCl: Na at the cathode, Cl₂ at the anode.
Core Concepts
- Metals lose electrons to become cations; non-metals gain electrons to become anions.
- A more reactive metal displaces a less reactive one from its salt solution.
- Ionic compounds: hard, brittle, high-melting, water-soluble, conduct only when molten or dissolved.
- The series decides the method: heat alone, carbon reduction, or electrolysis.
- Rusting needs both air and water; zinc protects iron even when its coat is broken.
Confused Pairs
- Mineral vs ore (profitably extracted).
- Roasting (sulphide, excess air) vs calcination (carbonate, limited air).
- Galvanising (zinc coat on iron) vs anodising (thicker oxide on aluminium).
- Malleable (sheets) vs ductile (wires).
- Brass (Cu + Zn) vs bronze (Cu + Sn).
- Amphoteric oxide vs basic oxide.
- Reserves vs mine production.
Data Points
- 1 g gold → about 2 km of wire.
- Table 3.4 melting points (K): NaCl 1074, LiCl 887, CaCl₂ 1045, CaO 2850, MgCl₂ 981.
- Steel: iron + about 0.05 % carbon (NCERT); aqua regia HCl : HNO₃ = 3 : 1.
- Iron pillar: more than 1600 years old, 8 m, 6 tonnes (NCERT).
- USGS 2026: rare-earth reserves China 44 Mt, Brazil 11 Mt, Australia 6.3 Mt, India not reported; mine output 2025e world 390,000 t, China 270,000 t, India 2,900 t.
- 30 critical minerals (24 July 2023); NCMM, 29 January 2025: Rs 16,300 crore + Rs 18,000 crore = Rs 34,300 crore over seven years.
PYQ Pattern
- Prelims: prelims-2026-gs1-060 (rare-earth elements and the National Critical Mineral Mission).
- No Mains question in the bank is set directly on this chapter's chemistry.
Sources
- NCERT, Science, Textbook for Class X, ch. 3 "Metals and Non-metals", Reprint 2026-27 — ncert.nic.in PDF.
- NCERT, Science, Class X, Answers, Reprint 2026-27 — ncert.nic.in PDF.
- NCERT, Science, Class X, 2020-21 edition (whole-book zip), as archived on 9 October 2021 — Wayback Machine.
- Indian Bureau of Mines, Indian Minerals Yearbook 2024 (63rd edition) — ibm.gov.in PDF.
- U.S. Geological Survey, Mineral Commodity Summaries 2026, "Rare Earths" — pubs.usgs.gov PDF.
- PIB (Ministry of Mines), "Thirty Critical Minerals List Released", 24 July 2023, Release ID 1942027 — pib.gov.in.
- PIB (Cabinet), "Cabinet Approves 'National Critical Mineral Mission'", 29 January 2025, Release ID 2097308 — pib.gov.in.
