Metals and Non-metals

Subject: General Science — Chemistry | Topic: Metals and Non-metals Exam: AP Group 2 (APPSC) | Sources: NCERT Class X, Lucent's GS

Introduction

Metals and non-metals covers physical/chemical properties, the reactivity series, extraction of metals, corrosion, and alloys. APPSC loves alloy compositions and the reactivity series — memorise both tables for guaranteed marks.

Physical Properties

Property	Metals	Non-metals
Hardness	Generally hard	Generally soft (Exception: Diamond — hardest)
Lustre	Shiny (lustrous)	Dull (Exception: Iodine — lustrous)
Malleability	Can be beaten into sheets (Gold — most malleable)	Brittle
Ductility	Can be drawn into wires (Platinum — most ductile)	Not ductile
Conductivity	Good conductors (Silver — best, Copper — 2nd)	Poor (Exception: Graphite conducts electricity)
State at room temp	Solid (Exception: Mercury — liquid)	Solid, liquid, or gas (Bromine — liquid)
Melting point	Generally high (Exception: Gallium, Caesium — low)	Generally low
Sonorous	Yes (ringing sound)	No
Density	Generally high (Exception: Na, K float on water)	Generally low

Chemical Properties of Metals

Metals + O₂ → Metal oxides (generally basic). Example: 4Na + O₂ → 2Na₂O
Amphoteric oxides (both acidic and basic): Al₂O₃, ZnO
Na/K react vigorously with water (stored in kerosene). Mg reacts with hot water. Fe reacts with steam. Cu, Ag, Au do not react.
More reactive metals displace less reactive metals from salt solutions.

Reactivity Series

K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > [H] > Cu > Hg > Ag > Au > Pt

Metals above hydrogen react with dilute acids to produce H₂ gas.
Metals below hydrogen (Cu, Hg, Ag, Au, Pt) do NOT react with dilute acids.
Gold and Platinum are the least reactive (noble metals) — found in native/free state in nature.

Extraction of Metals

Reactivity Level	Metals	Method
Highly reactive (top)	K, Na, Ca, Al	Electrolytic reduction
Moderately reactive (middle)	Zn, Fe, Pb	Reduction with carbon (smelting)
Least reactive (bottom)	Cu, Ag, Au	Simple heating or found free

Ore: Rock containing metal in sufficient quantity for extraction.
Roasting: Heating in excess air (sulphide ores). Calcination: Heating without air (carbonate ores).
Gangue: Impurities in ore removed by concentration/enrichment.

Corrosion and Prevention

Rusting: 4Fe + 3O₂ + water → 2Fe₂O₃·xH₂O (hydrated iron oxide, brown). Requires BOTH oxygen and water.

Prevention Method	Mechanism
Painting, oiling, greasing	Physical barrier
Galvanisation	Zinc coating; zinc corrodes first (sacrificial protection)
Electroplating	Thin metal coating
Alloying	Changes surface chemistry
Chromium plating	Resistant coating

Alloys

Alloy	Composition	Uses
Brass	Cu + Zn	Utensils, musical instruments
Bronze	Cu + Sn (tin)	Medals, statues, bells
Steel	Fe + C (0.05-1.5%)	Construction, tools
Stainless steel	Fe + Cr (10.5%+) + Ni + C	Cookware, surgical instruments
Solder	Pb + Sn	Joining electrical wires (low MP)
Amalgam	Mercury + another metal	Dental fillings
Duralumin	Al + Cu + Mg + Mn	Aircraft construction
German silver	Cu + Zn + Ni (NO silver)	Utensils, decorative items
Sterling silver	Ag (92.5%) + Cu	Jewellery

Rancidity

Oxidation of fats/oils giving bad smell and taste.
Prevention: antioxidants, airtight containers, refrigeration, nitrogen-filled packets, brown bottles.

Likely Exam Questions

The most malleable metal is: Ans: Gold
Which metal is liquid at room temperature? Ans: Mercury (Hg)
Galvanisation is coating iron with: Ans: Zinc
German silver contains: Ans: Copper, Zinc, and Nickel (no silver)
The least reactive metal in the reactivity series is: Ans: Platinum (Pt)
Rusting of iron requires: Ans: Both oxygen and water (moisture)
Brass is an alloy of: Ans: Copper and Zinc
Metals that are stored in kerosene are: Ans: Sodium and Potassium (react vigorously with water)
The process of heating ore in excess of air is called: Ans: Roasting
Non-metal that is a good conductor of electricity is: Ans: Graphite (a form of carbon)