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CC06 — Metals & Non-Metals

📖 CC06  ·  CDS General Science — Chemistry ★ High Priority

Metals and non-metals are the two broad categories of elements, each with characteristic physical and chemical properties. Metallurgy, alloys, and the reactivity series are directly and frequently tested in CDS.

📌 CDS Focus: Distinguishing physical properties (lustre, conductivity, malleability — metals; dull, brittle, poor conductors — non-metals); reactivity series (order matters for displacement reactions); corrosion of iron (rusting); important alloys (steel, brass, bronze, stainless steel); extraction methods (highly reactive metals → electrolysis; moderately reactive → reduction; low reactive → heating alone).

1. Physical Properties: Metals vs Non-Metals

Fig. 1 — Metals vs Non-Metals: Physical Properties Comparison
METALS vs NON-METALS — Physical Properties Property METALS NON-METALS Physical state Solid at room temp (except Hg) Solid, liquid, or gas Lustre Shiny / lustrous Dull (except iodine, diamond) Malleability Malleable (can be beaten flat) Brittle (break on hammering) Conductivity Good conductors (heat & electricity) Poor conductors (except graphite) Ductility Ductile (can be drawn into wires) Non-ductile Density & MP High density; high melting point Low density; low melting point (except Na, K — low density; Hg — liquid) (except carbon/diamond — very high MP)

2. Reactivity Series of Metals

Fig. 2 — Reactivity Series: Order from Most Reactive to Least Reactive
REACTIVITY SERIES — Most Reactive (Top) to Least Reactive (Bottom) Most Least HIGHLY REACTIVE → Extracted by ELECTROLYSIS K > Na > Ca > Mg > Al Potassium, Sodium, Calcium, Magnesium, Aluminium React vigorously with cold water; displace hydrogen gas. K & Na stored under kerosene (react explosively with water). MODERATELY REACTIVE → Extracted by REDUCTION (with C or CO) Zn > Fe > Ni > Sn > Pb Zinc, Iron, Nickel, Tin, Lead React with dilute acids; not with cold water. Iron most used industrial metal. — — — H₂ (Hydrogen divides metals above and below) — — — LEAST REACTIVE → Found FREE in nature or extracted by HEATING ALONE Cu > Hg > Ag > Au > Pt Copper, Mercury, Silver, Gold, Platinum. Do not react with dilute acids normally.

3. Important Alloys

AlloyMain MetalsProperties / Uses SteelIron + Carbon (0.2–2%)Strong, hard; construction, machinery, railways Stainless SteelFe + Cr (18%) + Ni (8%)Rust-resistant; kitchen utensils, surgical instruments BrassCopper + Zinc (30%)Musical instruments, decorative items, coins BronzeCopper + Tin (10–12%)Statues, coins, bearings, bells (harder than copper) DuraluminAl + Cu + Mg + MnAircraft construction (light and strong) SolderLead + Tin (60:40)Joining electrical wires (low melting point) German SilverCu + Zn + NiUtensils; contains no actual silver!
⚠ CDS Trap — Corrosion (Rusting of Iron):
Rusting requires BOTH oxygen AND water (moisture) — neither alone causes rusting. Chemically: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ (hydrated iron oxide = rust).
Prevention: painting, oiling, galvanising (zinc coating), alloying (making stainless steel), cathodic protection (sacrificial anode of zinc).

📝 CDS PYQs — Metals & Non-Metals

Q1. Which of the following is the best conductor of electricity among non-metals? CDS PYQ
(a) Diamond(b) Sulfur(c) Graphite(d) Phosphorus
✔ Answer: (c) Graphite
Graphite is the only non-metal that is a good conductor of electricity. In graphite, each carbon atom is bonded to three others in a hexagonal layer, leaving one free electron per carbon atom that can move and conduct electricity. Diamond, sulfur, and phosphorus are insulators. Graphite is used as electrodes in batteries and electrolysis.
Q2. Galvanising protects iron by coating it with: CDS PYQ
(a) Copper(b) Tin(c) Zinc(d) Nickel
✔ Answer: (c) Zinc
Galvanising is the process of coating iron with a layer of zinc to prevent rusting. Zinc acts as a sacrificial anode — it corrodes preferentially, protecting the iron even if the zinc coating is scratched. Used in: galvanised iron sheets, buckets, water tanks. Tin plating (tin cans) also protects but tin is cathodic to iron — once scratched, iron corrodes faster.
Q3. Brass is an alloy of: CDS PYQ
(a) Copper and Tin(b) Copper and Zinc(c) Iron and Carbon(d) Aluminum and Copper
✔ Answer: (b) Copper and Zinc
Brass = Copper (70%) + Zinc (30%). It is used for musical instruments, decorative items, and coins. Do not confuse with Bronze = Copper + Tin (used for statues, bells, bearings). This brass-vs-bronze distinction is a repeated CDS trap question.
Q4. Which metal is most reactive? CDS PYQ
(a) Iron(b) Sodium(c) Potassium(d) Aluminium
✔ Answer: (c) Potassium
Potassium (K) is the most reactive metal in the common reactivity series. It reacts explosively with water, and is stored under kerosene oil. The reactivity series order (common elements): K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > (H) > Cu > Hg > Ag > Au.

🧠 Quick Memory Chart — CC06

⚗ Reactivity Series
  • K > Na > Ca > Mg > Al
  • Zn > Fe > Ni > Sn > Pb
  • (H₂) > Cu > Hg > Ag > Au
  • Highly reactive → electrolysis
  • Low reactive → found free
⚛ Key Alloys
  • Steel: Fe + C
  • Brass: Cu + Zn (NOT tin)
  • Bronze: Cu + Sn (NOT zinc)
  • Solder: Pb + Sn (low MP)
  • Duralumin: Al + Cu (aircraft)
🚨 Key Traps
  • Graphite conducts (non-metal exception)
  • Mercury = liquid metal at room temp
  • Rusting needs O₂ + H₂O (both)
  • Galvanising = zinc coating on iron
  • German silver has NO silver

📝 Practice Exercise

E1. Which metal is stored under kerosene?
(a) Gold(b) Sodium(c) Iron(d) Copper
E2. Duralumin is used in aircraft because it is:
(a) Highly reactive(b) Light and strong(c) Cheap(d) Magnetic
E3. The process of coating iron with zinc is called:
(a) Anodising(b) Electroplating(c) Galvanising(d) Smelting
Answers: E1 → (b) Sodium [highly reactive; reacts with moisture in air; stored under kerosene]  |  E2 → (b) Light and strong [Al+Cu+Mg+Mn; ideal for aircraft]  |  E3 → (c) Galvanising [zinc coating by hot-dipping or electroplating]
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