Metals, Non-Metals and Reactivity
~9 min read
- Metals: Lustrous, ductile, malleable, sonorous, good conductors. Lose electrons (electropositive).
- Non-metals: Brittle, dull (except iodine), poor conductors (except graphite). Gain electrons (electronegative).
- Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au.
Metals are the lustrous half of the periodic table; non-metals are the dull other half. CDS/OTA tests their physical and chemical contrasts, the reactivity series and displacement reactions.
Metals vs Non-Metals
| Property | Metals | Non-metals |
|---|---|---|
| Appearance | Lustrous | Dull (except iodine) |
| State at room temp | Solid (except Hg) | Solid, liquid (Br) or gas |
| Conductivity | Good (heat, electricity) | Poor (except graphite) |
| Ductility | Ductile and malleable | Brittle |
| Sonority | Sonorous | Not sonorous |
| Density | Generally high | Low |
| Reaction with O₂ | Basic oxides (Na₂O, MgO) | Acidic oxides (CO₂, SO₂) |
| Reaction with acid | Reactive metals release H₂ | Generally no reaction |
Exceptions: Hg liquid metal; Br liquid non-metal. Iodine is a lustrous non-metal. Graphite (C) conducts electricity. Hydrogen is a non-metal placed in Group 1.
Reactivity Series
K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au
- K, Na — most reactive; stored under kerosene.
- Ca, Mg, Al — moderately reactive; react with steam.
- Zn, Fe — react with dilute acids releasing H₂.
- Cu, Hg, Ag, Au — below H; do not displace it from acids.
- Au is least reactive — used in jewellery and electronics for that reason.
Reactions of Metals
- With O₂: 4Na + O₂ → 2Na₂O. 2Cu + O₂ → 2CuO (black). Aluminium forms a protective oxide layer.
- With water: Reactive metals: 2Na + 2H₂O → 2NaOH + H₂. Less reactive metals react with steam (Mg + H₂O → MgO + H₂).
- With acid: Zn + dil. H₂SO₄ → ZnSO₄ + H₂.
- Displacement: A more reactive metal displaces a less reactive metal from its salt solution. Fe + CuSO₄ → FeSO₄ + Cu (blue solution turns green, brown deposit).
- Aluminothermite (thermite) reaction: 2Al + Fe₂O₃ → 2Fe + Al₂O₃ — releases intense heat, used to weld railway tracks.
Corrosion and Prevention
- Rusting of iron: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O (hydrated ferric oxide). Needs both O₂ and water.
- Prevention: painting, oiling, galvanising (zinc coat), electroplating, alloying, sacrificial anode (Mg/Zn block attached to iron pipelines/ships).
- Copper develops green patina (basic copper carbonate). Silver tarnishes black (Ag₂S). Aluminium forms an invisible protective oxide.
CDS/OTA PYQ Examples
Q: Most reactive metal among the following is:
(a) Sodium (b) Iron (c) Copper (d) Silver
Answer: (a) Sodium — Group 1, very high reactivity.
Q: Galvanisation is the process of coating iron with:
(a) Tin (b) Zinc (c) Copper (d) Aluminium
Answer: (b) Zinc.
Q: Which is the only liquid metal at room temperature?
(a) Bromine (b) Iodine (c) Mercury (d) Sodium
Answer: (c) Mercury.
Q: Aluminothermite welding uses:
(a) Al + CO₂ (b) Al + Fe₂O₃ (c) Al + ZnO (d) Fe + Al₂O₃
Answer: (b) Al + Fe₂O₃ — produces molten iron and Al₂O₃.
Q: Stored under kerosene to prevent reaction with air and moisture is:
(a) Iron (b) Copper (c) Sodium (d) Aluminium
Answer: (c) Sodium.
Drill Metals, Non-Metals and Reactivity for CDS/OTA
CDS/OTA-pattern items on Metals, Non-Metals and Reactivity with answer keys and explanations.
Start Free Mock TestFrequently Asked Questions
Why is sodium stored under kerosene?
Na reacts vigorously with both oxygen and moisture in air. Kerosene seals it from both, preventing combustion.
Why does aluminium not corrode despite being reactive?
On exposure to air, a thin tough layer of Al₂O₃ forms instantly on the surface, protecting the metal beneath from further reaction.
Why is gold used in jewellery and electronics?
Lowest reactivity — does not tarnish, corrode or oxidise. Highly ductile and a good conductor. Expensive but reliable for high-value contacts.