Metals and Non-metals

Why This Chapter Matters

8-10 marks in board exams. Reactivity series, extraction methods, alloys, and corrosion prevention are tested every year.

Prerequisites

•Chapter 1-2: Chemical reactions and types

•Atomic structure, electronic configuration

•Basic periodic table

Core Concepts

1. Physical Properties

Metals: Shiny, hard (except Na/K/Li), solid (except Hg), malleable, ductile, sonorous, good conductors.

Non-metals: Dull, soft, solid/liquid/gas, brittle, non-sonorous, poor conductors (except graphite).

2. Chemical Properties of Metals

With Oxygen:

2Mg + O2 -> 2MgO (burns bright white)

Al: forms protective Al2O3 layer (does not corrode further)

Gold, Platinum: do NOT react with oxygen

With Water:

Na: 2Na + 2H2O -> 2NaOH + H2 (very vigorous, may ignite)

Ca: Ca + 2H2O -> Ca(OH)2 + H2 (moderate)

Fe: 3Fe + 4H2O(steam) -> Fe3O4 + 4H2 (steam only)

Cu, Ag, Au: No reaction with water

With Acids:

Zn + 2HCl -> ZnCl2 + H2

Cu + HCl -> NO REACTION (Cu below H in reactivity series)

3. Reactivity Series

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

More reactive = displaces less reactive from salt solution.

4. Ionic Bond Formation

Metals lose electrons -> cations (+)

Non-metals gain electrons -> anions (-)

Na -> Na+ + e- | Cl + e- -> Cl-

Na+ + Cl- -> NaCl (ionic compound)

5. Extraction of Metals

High reactivity (K, Na, Ca, Mg, Al): Electrolysis (coke cannot reduce these)

Medium reactivity (Zn, Fe, Sn, Pb): Reduction with coke (smelting)

ZnO + C -> Zn + CO | Fe2O3 + 3CO -> 2Fe + 3CO2 (blast furnace)

Low reactivity (Cu, Hg, Ag, Au): Heating alone

2HgS + 3O2 -> 2HgO + 2SO2; 2HgO -> 2Hg + O2

Refining: Electrolytic refining — impure metal (anode) dissolves, pure metal deposits on cathode.

6. Corrosion and Alloys

Rusting: 4Fe + 3O2 + xH2O -> 2Fe2O3.xH2O (needs BOTH oxygen AND water)

Prevention: Painting, oiling, galvanising (zinc coating), tinning, electroplating, alloying.

Alloys:

•Brass: Cu + Zn (utensils)

•Bronze: Cu + Sn (statues, medals)

•Solder: Pb + Sn (joining metals, low melting point)

•Steel: Fe + C (construction)

•Stainless steel: Fe + C + Ni + Cr (cutlery)

•Duralumin: Al + Cu + Mg (aircraft)

Why alloys? Higher strength, lower reactivity, modified properties for specific uses.

PYQs

2023: State the principle of electrolytic refining. Which electrode is pure metal?

Impure metal (anode) dissolves in electrolyte, pure metal deposits on cathode.

2022: Why is sodium stored in kerosene?

Na reacts with water: 2Na + 2H2O -> 2NaOH + H2 (vigorous, can ignite).

Kerosene prevents contact with moisture and air.

2021: Give one example of: (a) liquid metal (b) non-metal that conducts electricity

(a) Mercury (Hg) | (b) Graphite

2020: Write equation for reaction of iron with steam. What type of oxide?

3Fe + 4H2O(steam) -> Fe3O4 + 4H2

Fe3O4 is a basic oxide (magnetic iron oxide).

MCQ Practice

Q1. Metal NOT reacting with cold water:

(A) Na (B) K (C) Mg (D) Ca

Answer: C (Mg reacts only with steam)

Q2. Al2O3 extraction method:

(A) Heating (B) Reduction with C (C) Electrolysis (D) Displacement

Answer: C

Q3 (Hard). Wire of resistance R stretched to double length. New resistance?

(A) R/2 (B) 2R (C) 4R (D) R/4

Answer: C [Length doubles (R=2R) + Area halves (R=2R again) = 4R total]

Revision Notes

METALS: shiny, malleable, ductile, sonorous, conduct electricity
NON-METALS: dull, brittle, poor conductors (except graphite)

REACTIVITY SERIES (top = most reactive):
K > Na > Ca > Mg > Al > Zn > Fe > H > Cu > Ag > Au

REACTIONS WITH WATER:
Na, K -> cold water (vigorous)
Ca -> cold water (moderate)
Mg, Al -> hot water or steam only
Fe -> steam only
Cu, Ag, Au -> no reaction

EXTRACTION:
High reactive -> Electrolysis
Medium -> Reduction with coke
Low -> Heating alone

CORROSION:
Rust = Fe2O3.xH2O (needs O2 AND water)
Prevention: painting, galvanising (Zn coating), alloying

ALLOYS: Brass(Cu+Zn), Bronze(Cu+Sn), Solder(Pb+Sn), Steel(Fe+C)