Metals and Alloys

1. General Physical Properties of Metals

• Lustrous (shiny), malleable (can be hammered into sheets), ductile (can be drawn into wires), good conductors of heat and electricity, generally solid at room temperature (exception: Mercury, liquid).
• Sonorous (produce a ringing sound when struck) — hence used in bells.
• High density and high melting/boiling points (exceptions: sodium, potassium are soft and low-melting).
• Silver and copper are the best conductors of electricity (silver > copper > gold > aluminium).

2. General Chemical Properties

• Metals lose electrons to form positive ions (cations) — they are electropositive.
• Reaction with oxygen: form basic oxides, e.g., 4Na + O₂ → 2Na₂O (metal oxides are generally basic; Al₂O₃ and ZnO are amphoteric — react with both acids and bases).
• Reaction with water: reactive metals (Na, K, Ca) react vigorously/violently with cold water releasing H₂; less reactive metals (Mg, Al, Zn, Fe) react with steam; Cu, Ag, Au do not react with water at all.
• Reaction with dilute acids: most metals release H₂ gas, except metals below hydrogen in the reactivity series (Cu, Ag, Au, Pt).
• Reaction with each other's salt solutions: a more reactive metal displaces a less reactive one from its salt solution (basis of the reactivity series).

3. The Reactivity Series (Most to Least Reactive)

K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au > Pt

Mnemonic commonly used: "Please Stop Calling Me A Zebra, Instead Try Hunting Cheap Hares (Silver And Platinum-Gold)" — corresponds to Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Tin, Hydrogen, Copper, mercury, Silver, Gold, Platinum. (Any equivalent mnemonic works — the order itself is what's tested.)

Significance: metals above hydrogen displace it from acids; metals higher in the series are extracted by more energy-intensive methods (electrolysis for K, Na, Ca, Mg, Al; reduction for Fe, Zn, Pb, Cu; found native for Ag, Au, Pt).

4. Metals, Non-metals, and Metalloids

• Metalloids (properties between metals and non-metals): Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Polonium.
• Non-metals important for comparison: generally poor conductors (except graphite), brittle if solid, form acidic or neutral oxides.
• Exceptions to remember: Graphite (a non-metal form of carbon) conducts electricity; Iodine is a lustrous non-metal; Diamond (carbon) is the hardest natural substance but a non-metal and non-conductor.

5. Occurrence and Extraction (Metallurgy Basics)

• Minerals: naturally occurring compounds of metals in the earth's crust.
• Ores: minerals from which metal can be extracted profitably.
• Common ores: Haematite (Fe₂O₃) and Magnetite (Fe₃O₄) for iron; Bauxite (Al₂O₃·2H₂O) for aluminium; Cinnabar (HgS) for mercury; Galena (PbS) for lead; Copper pyrites (CuFeS₂) for copper; Rock salt (NaCl) for sodium.
• Extraction steps (general): Crushing/grinding → Concentration (removing gangue) → Reduction (roasting/smelting or electrolysis) → Refining.
• Highly reactive metals (K, Na, Ca, Mg, Al) are extracted by electrolytic reduction of molten ores/salts.
• Moderately reactive metals (Fe, Zn, Pb, Cu) are extracted by reduction with carbon/carbon monoxide in a blast furnace.
• Least reactive metals (Ag, Au, Pt, Hg) occur in free/native state or are extracted by simple heating.

6. Rusting and Corrosion

• Rusting of iron: Fe reacts with oxygen and moisture to form hydrated iron(III) oxide (Fe₂O₃·xH₂O), a reddish-brown flaky substance.
• Conditions needed: presence of both oxygen AND moisture (water) — absence of either prevents rusting.
• Prevention methods: painting, oiling/greasing, galvanising (coating with zinc), chrome plating, alloying (making stainless steel), tin plating (used for food cans).
• Galvanisation: coating iron/steel with a layer of zinc to prevent rusting — zinc corrodes preferentially (sacrificial protection) even if the coating is scratched.
• Corrosion of other metals: Silver tarnishes (forms Ag₂S with sulphur compounds in air); Copper develops a green coating (basic copper carbonate) called patina, e.g., seen on the Statue of Liberty.

7. Alloys — Composition and Uses (High-Yield Table)

An alloy is a homogeneous mixture of two or more metals (or a metal and a non-metal like carbon) designed to enhance properties like strength, hardness, or corrosion resistance.

Alloy	Composition	Key Property/Use
Stainless steel	Fe + Cr + Ni (+ small C)	Corrosion-resistant, used in utensils, surgical instruments
Brass	Cu + Zn	Corrosion-resistant, used in musical instruments, fittings
Bronze	Cu + Sn (tin)	Hard, used in statues, medals, bells
Bell metal	Cu + Sn (higher Sn than bronze)	Sonorous, used for bells
Gun metal	Cu + Sn + Zn	Used for guns, machine parts
Duralumin	Al + Cu + Mg + Mn	Light and strong, used in aircraft bodies
Solder	Pb + Sn	Low melting point, used for soldering/joining wires
Amalgam	Any metal + Mercury	Used in dentistry (silver amalgam for fillings), thermometers
Invar	Fe + Ni	Very low thermal expansion, used in precision instruments
Nichrome	Ni + Cr + Fe	High resistance, used in heating elements (electric heaters, toasters)
German silver	Cu + Zn + Ni (no actual silver)	Used in utensils, musical instruments
Rolled gold / Alnico	Al + Ni + Co (+ Fe)	Used to make strong permanent magnets
Magnalium	Al + Mg	Light alloy used in aircraft, laboratory instruments
Monel metal	Ni + Cu	Corrosion-resistant, used in marine/chemical equipment
Pewter	Sn + Cu + Sb	Used for tableware, decorative items
Rose metal	Bi + Pb + Sn	Low melting point, used in fire sprinklers/safety devices
Wood's metal	Bi + Pb + Sn + Cd	Very low melting point (~70°C), used as fuse metal

8. Special Notes and Frequently Tested Facts

• Most abundant metal in Earth's crust: Aluminium. Most abundant metal overall in Earth (including core): Iron.
• Most malleable and ductile metal: Gold.
• Metal that exists as liquid at room temperature: Mercury.
• Lightest metal: Lithium. Densest naturally occurring metal: Osmium (with Iridium very close).
• Softest metal (can be cut with a knife): Sodium and Potassium (also Caesium).
• 24-carat gold is pure gold (too soft for jewellery); ornamental gold is usually 22-carat (22 parts gold, 2 parts copper/silver alloy) for hardness.
• Stainless steel does not rust because chromium forms a thin protective oxide layer on the surface.
• Tungsten has the highest melting point among metals (~3422°C) — used in light bulb filaments.
• Aluminium is preferred for aircraft/utensils because it is light, corrosion-resistant (forms a protective oxide layer) and a good conductor.
• Sodium metal is stored under kerosene oil because it reacts violently with moisture/air.

9. Iron and Steel Metallurgy in Detail (UPSC/Higher-Level Additions)

• Blast furnace process: Iron ore (haematite/magnetite) is reduced using coke (carbon) and limestone (flux, removes impurities as slag) at high temperature to produce pig iron (crude iron, ~4% carbon, brittle).
• Pig iron is refined into:
• Cast iron (2–4% carbon): hard, brittle, used for pipes, manhole covers.
• Wrought iron (almost pure, <0.25% carbon): malleable, ductile, used for decorative work, chains.
• Steel (0.25–2% carbon): the most useful form — strength and malleability balanced, alloyed further (with Cr, Ni, Mn, V) for special properties (stainless steel, high-speed steel, etc.).
• India's major integrated steel plants (public sector, under SAIL): Bhilai (Chhattisgarh), Durgapur & Burnpur/IISCO (West Bengal), Bokaro (Jharkhand), Rourkela (Odisha) — a classic static-geography fact frequently paired with questions on India's steel policy, National Steel Policy 2017, and PLI (Production-Linked Incentive) schemes for specialty steel.
• India is among the world's top crude steel producers, and steel/metals feature heavily in Mains GS3 (infrastructure, industrial policy, mineral resources).

10. Aluminium and Non-Ferrous Metallurgy

• Bauxite → Alumina → Aluminium: Bauxite ore is refined to alumina (Al₂O₃) via the Bayer process, then alumina is electrolysed (Hall-Héroult process) to obtain aluminium metal — an energy-intensive process, which is why aluminium smelters are located near cheap power sources (e.g., hydroelectric or captive thermal power).
• Major Indian bauxite reserves: Odisha (largest), followed by Andhra Pradesh, Gujarat, Jharkhand, Chhattisgarh — recurring in economic geography questions.
• Copper smelting and India's major copper belts (Khetri in Rajasthan, Malanjkhand in Madhya Pradesh, Singhbhum in Jharkhand) are similarly tested alongside mineral-policy questions (National Mineral Policy, MMDR Act amendments).

11. UPSC Angle: Static-Dynamic Linkages

• Critical and strategic minerals (lithium, cobalt, nickel, rare earths, copper) needed for EV batteries and green-energy transition are a very live Mains GS3/Prelims theme — link this to India's push for domestic lithium exploration (Jammu & Kashmir's Salal-Haimana lithium find, 2023) and the Critical Mineral Mission.
• Mining sector reforms: MMDR (Mines and Minerals Development and Regulation) Amendment Acts, auction-based allocation of mineral blocks, and National Mineral Exploration Trust (NMET) are dynamic policy layers built on the static ore/metal facts above.
• Recycling and circular economy: e-waste is a growing "urban mine" for metals like gold, copper, and rare earths — connects metallurgy to environmental policy (E-Waste Management Rules) and the circular economy theme popular in Mains GS3 answers.
• PLI scheme for specialty steel (2021) and National Steel Policy 2017 targets (300 million tonnes capacity by 2030-31) are dynamic facts worth pairing with the static blast-furnace/steel-type knowledge above.

12. PYQ-Style Practice Pointers

• SSC/RRB pattern: "Which is the most malleable/ductile metal?" (Gold) — a very frequently repeated one-liner across multiple exam cycles.
• SSC/RRB pattern: matching alloys to their composition (brass=Cu+Zn, bronze=Cu+Sn, stainless steel=Fe+Cr+Ni) — the single highest-yield table in this entire topic; expect at least one direct question per exam cycle.
• UPSC Prelims pattern: statement-based questions combining ore names (bauxite, haematite, galena) with the metal extracted and the Indian state where it is chiefly mined — a classic "match the following" trap requiring both chemistry and geography recall together.

13. Practice Questions (With Answers)

SSC/RRB style (direct recall):

1. Which of the following is the most malleable and ductile metal? (a) Silver (b) Gold (c) Copper (d) Aluminium Answer: (b) Gold

2. Brass is an alloy of: (a) Copper and Tin (b) Copper and Zinc (c) Copper and Nickel (d) Iron and Chromium Answer: (b) Copper and Zinc

3. Which metal is stored under kerosene oil? (a) Iron (b) Sodium (c) Zinc (d) Copper Answer: (b) Sodium — it reacts violently with moisture/air.

4. Stainless steel resists rusting mainly because of the presence of: (a) Nickel (b) Carbon (c) Chromium (d) Manganese Answer: (c) Chromium — forms a protective oxide layer.

5. Galvanisation involves coating iron with: (a) Tin (b) Zinc (c) Chromium (d) Copper Answer: (b) Zinc

UPSC Prelims style (statement-based/applied):

6. Consider the following statements regarding the reactivity series of metals:
7. Metals higher in the reactivity series than hydrogen can displace hydrogen from dilute acids.

8. Gold and Platinum occur in nature mostly in their native (free) state. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 Answer: (c) Both 1 and 2

9. With reference to the extraction of aluminium, consider the following statements:

10. Bauxite ore is first converted to alumina by the Bayer process.

11. Alumina is then reduced to aluminium metal by the Hall-Héroult electrolytic process. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 Answer: (c) Both 1 and 2

12. Odisha is the largest producer of which of the following ores in India? (a) Bauxite (b) Copper (c) Manganese (d) Mica Answer: (a) Bauxite