Why this chapter matters for UPSC: Metals and non-metals underpin UPSC questions on mineral resources, critical minerals policy, industrial development, environmental pollution (heavy metal contamination), and material science. India's push for critical mineral security — lithium, cobalt, rare earth elements — is a direct GS3 topic.

PART 1 — Quick Reference Tables

Property Metals Non-metals
Physical state (room temp) Mostly solid (except mercury — liquid) Solid, liquid (bromine), or gas
Lustre Shiny / lustrous Mostly dull (except iodine — some lustre)
Hardness Generally hard (except sodium, potassium — soft) Mostly soft (except diamond — hardest natural substance)
Malleability Yes — beaten into sheets No — brittle (break on hammering)
Ductility Yes — drawn into wires No
Sonority Yes — produce ringing sound No
Conductivity (heat) Good conductors Poor conductors (except graphite)
Conductivity (electricity) Good conductors Poor conductors (except graphite)
Oxide nature Basic oxides (turn red litmus blue) Acidic oxides (turn blue litmus red)
Examples Iron, copper, aluminium, gold, silver, zinc Carbon, sulphur, nitrogen, oxygen, chlorine, iodine
Metal Key Properties Main Uses
Iron (Fe) Strong, magnetic, rusts in presence of air + water Construction, machinery, vehicles
Copper (Cu) Excellent conductor, ductile, non-magnetic Electrical wiring, plumbing, coins
Aluminium (Al) Light, malleable, corrosion-resistant Aircraft, packaging, utensils, overhead cables
Gold (Au) Unreactive, malleable, lustrous Jewellery, electronics, investment
Silver (Ag) Best conductor, antimicrobial Jewellery, mirrors, electronics
Zinc (Zn) Galvanisation of iron Galvanised iron sheets, batteries
Mercury (Hg) Only liquid metal at room temperature Thermometers (being phased out), barometers
Critical Mineral Use India's Status
Lithium EV batteries, electronics No significant domestic reserves; importing
Cobalt EV batteries, aerospace alloys Minimal domestic production
Rare Earth Elements (REEs) Electronics, defence, wind turbines India has significant deposits (Monazite sands in Kerala, Odisha, Tamil Nadu)
Nickel Stainless steel, batteries Limited reserves in Odisha
Platinum Group Metals Catalytic converters, fuel cells Negligible domestic reserves

PART 2 — Detailed Notes

Key Term

Malleability: The property of metals to be beaten or rolled into thin sheets without breaking. Example: gold can be beaten into extremely thin sheets (gold foil/leaf); aluminium foil used for food packaging.

Ductility: The property of metals to be drawn into thin wires. Example: copper and aluminium are drawn into electrical wires; gold can be drawn into very thin wire.

Sonority: The property of metals to produce a ringing sound when struck. Example: bells are made of metals (bronze = copper + tin); school bells, church bells.

Conductivity: Metals are good conductors of both heat and electricity because they have free electrons. Non-metals (except graphite) are insulators.

Corrosion: The gradual deterioration of a metal due to chemical reaction with its environment (usually oxygen and moisture). Rusting of iron is the most common form. Iron + Oxygen + Water → Iron Oxide (rust, Fe₂O₃·xH₂O). Rusting requires BOTH oxygen and water — tested frequently.

Galvanisation: Coating iron with a thin layer of zinc to prevent rusting. Zinc is more reactive than iron — it acts as a sacrificial anode, corroding preferentially.

Alloys: Homogeneous mixtures of a metal with other metals or non-metals. Examples: Steel (iron + carbon), Stainless Steel (iron + carbon + chromium + nickel), Bronze (copper + tin), Brass (copper + zinc).

UPSC Connect

India's Critical Minerals Policy

The Ministry of Mines released India's Critical Minerals List (2023) — 30 minerals identified as critical for economic development, national security, and energy transition. These include lithium, cobalt, graphite, nickel, manganese, REEs, and titanium.

Key Initiatives:

  • Khanij Bidesh India Limited (KABIL): JV of NALCO, HCL, and MECL to acquire strategic mineral assets overseas (lithium in Argentina, cobalt in Australia/Africa)
  • Mines and Minerals (Development and Regulation) Amendment Act, 2023: Allowed central government to auction mining leases for critical minerals (previously reserved for state governments for some minerals)
  • National Mineral Policy 2019: Promotes ease of mining, sustainable resource use, mineral security
  • Rare Earth Elements: India has the world's 5th largest REE reserves (estimated 6.9 million tonnes). Thorium-bearing Monazite sand in coastal states — regulated by Department of Atomic Energy due to radioactivity of thorium.

Environmental Concerns with Mining:

  • Heavy metal contamination of soil and water (lead, mercury, cadmium, arsenic)
  • The Minamata disease (Japan, 1950s) — caused by mercury poisoning from industrial discharge → Minamata Convention on Mercury (2013); India ratified in 2018
  • Lead in paint and petrol (now banned in India — unleaded petrol since 2000)
Explainer

Rusting — A UPSC Trap Zone

Rusting of iron requires BOTH oxygen AND moisture. Neither alone causes rusting:

  • Iron in dry air: no rust (no water)
  • Iron in boiled (de-oxygenated) water under oil: no rust (no oxygen)
  • Iron in normal moist air: rusts

Prevention methods:

  1. Painting/varnishing: Physical barrier to oxygen and water
  2. Galvanisation: Zinc coating (zinc = more reactive, sacrifices itself)
  3. Tin plating: Used for food cans (tin is less reactive than iron but weaker protection than zinc — if tin layer breaks, iron rusts faster)
  4. Alloying: Stainless steel (chromium forms a protective oxide layer)
  5. Greasing/oiling: Machinery components lubricated to prevent moisture contact

Metal Oxides — Acid-Base Chemistry Connection: When metals burn in oxygen, they form basic oxides:

  • 2Mg + O₂ → 2MgO (magnesium oxide — basic, turns red litmus blue) When non-metals burn in oxygen, they form acidic oxides:
  • S + O₂ → SO₂ (sulphur dioxide — forms sulphurous acid with water → acid rain)
  • This connects Chapter 4 with Chapter 2 (acids and bases) and Chapter 5 (chemical changes)

Diamond and Graphite — Same Element, Different Properties: Both are forms (allotropes) of carbon (non-metal):

  • Diamond: hardest natural substance; insulator; transparent; used in cutting tools
  • Graphite: soft; good conductor; used as lubricant, electrode, pencil lead This illustrates that the form/structure of atoms matters as much as composition.

Exam Strategy

  • Rusting needs BOTH oxygen AND water — not just one. Common Prelims trap: "which condition is sufficient to prevent rusting" — answer is preventing either oxygen or moisture access.
  • Mercury is the only metal that is liquid at room temperature. Gallium melts slightly above room temperature (~30°C) — not usually tested at Class 7 level.
  • Graphite (non-metal carbon) conducts electricity — exception to the rule that non-metals are insulators.
  • Diamond (non-metal carbon) is the hardest natural substance — not a metal.
  • Know the difference between galvanisation (zinc coating) and tin plating (tin coating) — galvanisation is more protective because zinc is sacrificial.
  • KABIL (Khanij Bidesh India Ltd.) — for acquiring critical mineral assets abroad. Distinguish from NALCO, HCL, MECL (which are component companies of KABIL).
  • The Minamata Convention (2013, entered into force 2017) targets mercury — named after Minamata disease in Japan caused by organic mercury.

Previous Year Questions

Q1. Rusting of iron occurs when iron is exposed to:
(a) Only oxygen
(b) Only water/moisture
(c) Both oxygen and water/moisture
(d) Only carbon dioxide

(c) Both oxygen and water/moisture

Q2. Which of the following statements about diamond and graphite is correct?
(a) Diamond is a metal; graphite is a non-metal
(b) Both diamond and graphite are allotropes of carbon
(c) Diamond conducts electricity; graphite does not
(d) Diamond is harder than graphite because it contains more carbon atoms

(b) Both diamond and graphite are allotropes of carbon

Q3. Consider the following with reference to critical minerals in India:

  1. India has significant Rare Earth Element deposits in its coastal monazite sands.
  2. KABIL is a joint venture formed to acquire critical mineral assets abroad.
  3. Lithium is not included in India's Critical Minerals list.

Which of the statements given above is/are correct?
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3

(b) 1 and 2 only