Metals, Non-Metals and Alloys
~9 min read
- Metals: Lustrous, malleable, ductile, conduct heat/electricity, sonorous, high density, mostly solids (except Hg). Examples: Fe, Cu, Al, Au, Ag.
- Non-metals: Dull, brittle, non-conducting, mostly low density. Solid/liquid/gas. Examples: C, S, P, O, N.
- Alloys: Mixtures of metals (sometimes with non-metals). Better properties than pure metal. Brass, bronze, steel, stainless steel.
Most NDA Chemistry questions on materials test metal/non-metal properties and common alloys.
Comparison of Metals and Non-Metals
| Property | Metals | Non-Metals |
|---|---|---|
| Lustre | Lustrous (shiny) | Dull (except diamond, iodine) |
| Malleability | Malleable (can be hammered into sheets) | Brittle (break when struck) |
| Ductility | Ductile (can be drawn into wires) | Not ductile |
| Conductivity | Good conductors of heat and electricity | Insulators (except graphite) |
| State at room temp. | Solid (except mercury — liquid) | Solid, liquid (Br) or gas (O₂, N₂) |
| Sonorous | Yes (ring when struck) | No |
| Density | High (Pb, W high; Li, Na low) | Generally lower |
| Reaction with acids | React, release H₂ (active metals) | Generally don't react |
| Oxides | Basic / amphoteric | Acidic |
Reactivity Series
Metals arranged in decreasing order of reactivity:
K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au
- More reactive metals displace less reactive metals from their salt solutions.
- Active metals (K, Na, Ca) react with cold water vigorously.
- Less active metals (Cu, Ag, Au) don't react with water or dilute acids.
- Au is most unreactive ("noble metal") — found native in nature.
Common Alloys
| Alloy | Composition | Use |
|---|---|---|
| Brass | Cu (70%) + Zn (30%) | Decorative items, locks, taps, electrical contacts |
| Bronze | Cu (90%) + Sn (10%) | Coins, statues, medals, bells |
| Steel | Fe + C (~0.2-2%) | Construction, machinery, vehicles |
| Stainless steel | Fe + Cr (18%) + Ni (8%) | Cutlery, utensils, surgical instruments |
| Duralumin | Al + Cu + Mg + Mn | Aircraft body, light + strong |
| Magnalium | Al + Mg | Light structural parts |
| Solder | Pb + Sn | Joining electrical wires, plumbing |
| Amalgam | Hg + other metal | Dental fillings (Hg + Ag historically); sodium amalgam in industry |
| German silver | Cu + Zn + Ni (no Ag despite name) | Decorative items, cutlery |
| Gunmetal | Cu + Sn + Zn | Cannon barrels, machine parts |
| Bell metal | Cu (78%) + Sn (22%) | Bells, gongs |
| Constantan | Cu + Ni | Resistance wire, thermocouples |
| Pewter | Sn (85-95%) + Pb/Sb/Cu | Decorative ware |
| Nichrome | Ni + Cr + Fe | Heating elements (toaster, electric heater) |
Properties of Common Metals
- Iron (Fe): Most-used metal. Rusts unless protected.
- Copper (Cu): Excellent conductor. Used in wiring, plumbing, alloys.
- Aluminium (Al): Light, corrosion-resistant (Al₂O₃ layer protects). Used in aircraft, foil, utensils.
- Gold (Au): Unreactive, ductile. Jewellery, electronic contacts. Purity: 24 carat = pure.
- Silver (Ag): Best electrical conductor. Jewellery, mirrors, coins, electronics.
- Mercury (Hg): Only liquid metal at room T. Thermometers (declining), barometers, dental amalgam.
- Lithium (Li): Lightest metal. Modern batteries (Li-ion).
- Tungsten (W): Highest melting point (3422°C). Light bulb filaments, drill bits.
- Sodium (Na): So reactive that it must be stored under kerosene. Used in street lamps (vapour lamps), nuclear coolants.
NDA PYQ Examples
Q: Which is a liquid metal at room temperature?
(a) Bromine (b) Mercury (c) Sodium (d) Lithium
Answer: (b) Mercury — only liquid metal at room T.
Q: Stainless steel contains iron with:
(a) Cu and Zn (b) Cr and Ni (c) Sn and Pb (d) Mg and Al
Answer: (b) Cr (~18%) and Ni (~8%).
Q: Brass is an alloy of:
(a) Cu and Sn (b) Cu and Zn (c) Fe and C (d) Pb and Sn
Answer: (b) Copper and Zinc.
Q: The lightest metal is:
(a) Sodium (b) Lithium (c) Aluminium (d) Hydrogen
Answer: (b) Lithium — density 0.534 g/cm³.
Q: Bronze is an alloy of:
(a) Cu + Zn (b) Cu + Sn (c) Cu + Ni (d) Fe + Cr
Answer: (b) Copper and Tin.
Drill Metals, Non-Metals and Alloys for NDA
NDA-pattern items on Metals, Non-Metals and Alloys with answer keys and explanations.
Start Free Mock TestFrequently Asked Questions
Why is gold called a noble metal?
Gold doesn't react with most common substances — doesn't tarnish in air, doesn't rust in moisture, only attacked by very strong acid mixtures (aqua regia: HCl + HNO₃ in 3:1 ratio). 'Noble' for its chemical aloofness.
Why is sodium stored under kerosene?
Sodium reacts vigorously with both moisture and oxygen in air (forming sodium hydroxide and oxide). Kerosene is non-polar; sodium doesn't react with it. Storage under kerosene isolates sodium from air and water.
What makes stainless steel rust-resistant?
Chromium (~18%) forms a thin invisible Cr₂O₃ layer on the surface. This passive oxide layer prevents oxygen and moisture from reaching the iron underneath. If scratched, the chromium oxide reforms — self-healing protection.
Why is aluminium used for aircraft?
Aluminium and its alloys (especially duralumin: Al + Cu + Mg + Mn) are lightweight (~1/3 the weight of steel) yet strong enough. Also corrosion-resistant due to natural Al₂O₃ film. Aircraft prioritise strength-to-weight ratio.
What is 24-carat gold?
Pure gold (99.9%). 24 = pure; 18 carat = 18/24 = 75% gold (mixed with Cu, Ag for strength); 14 carat = 14/24 = 58.3%; etc. Higher carat = softer; lower carat = harder, more durable.