Summary and Quick Revision

Chapter 3 — Summary and Quick Revision

Just before the board exam — quick overview of the entire chapter.

Metals and Non-Metals — Basic Differences

Property	Metal	Non-metal
Physical state	Mostly solid	All states
Lustre	Metallic	Mostly no
Malleability	Yes	No
Ductility	Yes	No
Conductivity	Good	Poor
Sonority	Yes	No

Major Exceptions:

• Hg: liquid metal.
• I₂: lustrous non-metal.
• Graphite: conducting non-metal.

Important Chemical Reactions

1. Metal + Oxygen → Metal Oxide (Basic)

$$2Mg + O_2 \rightarrow 2MgO$$ $$4Al + 3O_2 \rightarrow 2Al_2O_3$$ $$3Fe + 2O_2 \rightarrow Fe_3O_4$$

2. Metal + Water → Hydroxide + H₂

With cold water: $2Na + 2H_2O \rightarrow 2NaOH + H_2$ With steam: $3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$

3. Metal + Acid → Salt + H₂

$$Zn + 2HCl \rightarrow ZnCl_2 + H_2$$

4. Displacement Reaction

$$Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$$

Reactivity Series (Essential!)

More to less reactive:

$$\boxed{K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au}$$

Mnemonic: 'Please Stop Calling Me A Zebra Instead Try Learning How Copper Saves Gold'

Three Categories — and Extraction

Category	Metals	Extraction
High	K, Na, Ca, Mg, Al	Electrolysis
Moderate	Zn, Fe, Pb	Reduction by C
Low	Hg, Cu, Ag, Au	Direct heating

Practical Use of Series

1. Storage:

• Na, K → in kerosene.
• Others → in open.

2. Reaction with acids:

• Above H → release H₂.
• Below H → no reaction.

3. Displacement:

• More reactive → displaces less reactive.

4. Extraction Method:

• Reactivity decides.

Ionic Compounds — At a Glance

Formation

Metal → loses electrons (cation). Non-metal → gains electrons (anion). Opposite charges → ionic bond.

Important Ions

Metal	Ion	Configuration
Na	Na⁺	(2,8)
Mg	Mg²⁺	(2,8)
Al	Al³⁺	(2,8)
Ca	Ca²⁺	(2,8,8)

Non-metal	Ion	Configuration
Cl	Cl⁻	(2,8,8)
O	O²⁻	(2,8)
N	N³⁻	(2,8)

Find Formula — Cross-Multiplication

Al³⁺ + O²⁻ → Al₂O₃ Mg²⁺ + N³⁻ → Mg₃N₂ Na⁺ + S²⁻ → Na₂S Ca²⁺ + PO₄³⁻ → Ca₃(PO₄)₂

5 Properties of Ionic Compounds

1. Solid state: hard, crystalline, brittle.
2. High melting point: NaCl 801°C, MgO 2852°C.
3. Soluble in water.
4. Insoluble in kerosene.
5. Electrical conductivity: Solid — No; Molten/aqueous — Yes.

Extraction — Complete Process

Three Steps

1. Concentration (Section 6)
   ↓
2. Reduction (Section 7)
   ↓
3. Refining (Section 8)

4 Methods of Concentration

Method	For Whom
Hand picking	Visual difference
Gravity	Density difference
Magnetic	Magnetic property
Froth flotation	Sulphide ores

Important Ores

Metal	Ore	Formula
Al	Bauxite	Al₂O₃·2H₂O
Fe	Hematite	Fe₂O₃
Fe	Magnetite	Fe₃O₄
Cu	Copper pyrites	CuFeS₂
Zn	Zinc blende	ZnS
Hg	Cinnabar	HgS
Pb	Galena	PbS

Roasting vs Calcination

Property	Roasting	Calcination
Ore	Sulphide	Carbonate
Air	Yes	No
Example	$2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$	$ZnCO_3 \rightarrow ZnO + CO_2$

Main Extraction Processes

1. Fe — Blast Furnace

Reactions:

• $C + O_2 \rightarrow CO_2$
• $CO_2 + C \rightarrow 2CO$
• Main: $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
• $CaCO_3 \rightarrow CaO + CO_2$
• $CaO + SiO_2 \rightarrow CaSiO_3$ (slag)

Products: Pig iron + slag.

2. Al — Hall-Héroult

Bayer Process:

• $Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$

Hall-Héroult:

• Al₂O₃ + cryolite (Na₃AlF₆) → 950°C.
• Cathode: $Al^{3+} + 3e^- \rightarrow Al$
• Anode: $2O^{2-} \rightarrow O_2 + 4e^-$

Overall: $2Al_2O_3 \xrightarrow{\text{electricity}} 4Al + 3O_2$

3. Na — Down's Cell

Electrolysis of molten NaCl.

• Cathode: Na
• Anode: Cl₂

Cl₂ — bonus product (NaOH also in aqueous).

4. Hg — Simple Method

• $2HgS + 3O_2 \rightarrow 2HgO + 2SO_2$
• $2HgO \rightarrow 2Hg + O_2$

5. Cu — Self-Reduction

• $2CuFeS_2 + 3O_2 \rightarrow 2Cu_2S + 2FeO + 2SO_2$
• $2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$

Corrosion and Protection

Corrosion Products

Metal	Layer	Formula	Nature
Fe	Rust	Fe₂O₃·xH₂O	Harmful
Cu	Patina	Cu(OH)₂·CuCO₃	Protective (green)
Ag	Tarnish	Ag₂S	Surface (black)
Al	Oxide	Al₂O₃	Protective

Required for Rust

Both: Water + Oxygen.

Reaction: $$4Fe + 3O_2 + xH_2O \rightarrow 2Fe_2O_3 \cdot xH_2O$$

7 Methods of Prevention

1. Paint (cheap).
2. Oil/grease (immediate).
3. Galvanisation (Zn coating — Cathodic protection).
4. Cr plating (shiny).
5. Electroplating (thin layer).
6. Anodising (on Al).
7. Alloy (stainless steel).

Electrolytic Refining (Cu Example)

• Anode: impure Cu.
• Cathode: pure Cu.
• Solution: CuSO₄ + H₂SO₄.

In anode mud: Au, Ag, Pt (valuable!).

Alloys — At a Glance

Name	Composition	Use
Stainless	Fe + Cr + Ni	Utensils
Brass	Cu + Zn	Decoration
Bronze	Cu + Sn	Statues
Solder	Pb + Sn	Welding
Duralumin	Al + Cu + Mg + Mn	Aircraft
Amalgam	Hg + others	Dentistry

🧠 Board Tips — Frequently Asked

Essential Reactions

Memorise by writing:

1. Mg + O₂: $2Mg + O_2 \rightarrow 2MgO$
2. Na + H₂O: $2Na + 2H_2O \rightarrow 2NaOH + H_2$
3. Zn + HCl: $Zn + 2HCl \rightarrow ZnCl_2 + H_2$
4. Zn + CuSO₄: $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$
5. Fe + steam: $3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$
6. Al₂O₃ + NaOH: $Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$
7. Al + Fe₂O₃: $2Al + Fe_2O_3 \rightarrow Al_2O_3 + 2Fe$ (thermite)
8. Rust: $4Fe + 3O_2 + xH_2O \rightarrow 2Fe_2O_3 \cdot xH_2O$
9. Roasting: $2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$
10. Blast Furnace: $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$

Essential Definitions

Term	Definition
Mineral	Natural compound
Ore	Mineral suitable for metal extraction
Gangue	Unwanted impurity
Flux	Chemical for removing gangue
Slag	Flux + gangue
Roasting	Sulphide + air
Calcination	Carbonate heated
Anodising	Thicker $Al_2O_3$ on Al
Galvanisation	Zn on Fe
Patina	Green layer on Cu
Tarnish	Black layer on Ag
Aqua regia	HCl + HNO₃ (3:1)
Thermite	Al + Fe₂O₃
Alloy	Mixture of metals

Essential Diagrams

1. Blast Furnace. 2. Hall-Héroult cell. 3. Electrolytic refining. 4. Three test tubes (rust experiment). 5. Reactivity series.

🚀 Final Table — Whole Chapter on One Page

Physical Properties

Metal: lustrous, malleable, ductile, conducting, sonorous. Non-metal: opposite.

Chemical Properties

Metal:

• With O₂ → basic oxide
• With acid → salt + H₂
• With water → hydroxide + H₂
• Displacement (per series)

Reactivity Series

$$K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au$$

Ionic Compound

Metal + Non-metal = Ionic.

• Na + Cl → NaCl
• Mg + Cl → MgCl₂
• Ca + O → CaO

Steps of Extraction

1. Concentration (4 methods). 2. Reduction (3 methods — by reactivity). 3. Refining (electrolytic).

Major Extractions

1. Fe → Blast Furnace. 2. Al → Hall-Héroult. 3. Na → Down's cell. 4. Cu → self-reduction. 5. Hg → direct heating.

Corrosion and Protection

Rust = $Fe_2O_3 \cdot xH_2O$. Required: H₂O + O₂.

7 prevention methods: paint, oil, galvanisation, Cr plating, electroplating, anodising, alloys.

Alloys

Stainless = Fe + Cr + Ni. Brass = Cu + Zn. Bronze = Cu + Sn. Solder = Pb + Sn. Duralumin = Al + Cu + Mg + Mn.

Final Formulas

'Reactivity ↑ → extraction difficulty ↑.' 'Metal + Non-metal = Ionic.' 'Metal + Metal = Alloy.' 'Rust = water + air + iron.' 'Galvanisation = Cathodic protection.'

All the best for board exams!

📋 Board Exam Strategy — Chapter 3

Question Paper Pattern (CBSE Class 10)

Types of questions:

1-mark questions (MCQ/very short):

• Major metals, ores, formulas.
• Reactivity order.
• One-line definitions.

2-3 mark questions:

• One reaction + observation.
• One numerical.
• Difference between two.

5-mark questions:

• One process (like Blast Furnace).
• Mixed question (from many topics).
• Explanation with diagram.

Weight of Chapter 3 in Question Paper

Average CBSE 10:

• Total: 5-6 marks.
• 1-2 questions of 1-mark.
• 1 question of 3-mark.
• 1 question of 5-mark (sometimes).

Most Frequently Asked

Top 5 PYQs:

1. Reactivity series + practical use.
2. Fe extraction (Blast Furnace).
3. Al extraction (Hall-Héroult).
4. Rust and prevention.
5. Ionic compound formation.

Tips to Score Better

1. Always draw diagrams. Blast Furnace, Hall-Héroult, refining — incomplete without diagrams.

2. Keep reactions balanced. Unbalanced = marks deducted. Write states (s), (l), (g), (aq).

3. Write observations. Not just reaction — observations too. Examples: blue colour, bubbles, flame.

4. Detailed answers. 5-mark question = at least 8-10 points. Use sub-headings.

Final Tip — Day of Exam

1. Revise reactivity series once. 2. Memorise 5 essential reactions. 3. Practise one PYQ. 4. Go with confidence!

All the best! 🎓

📚 Selected NCERT Textbook Questions — Solutions

Q1: Why is magnesium ribbon rubbed with sandpaper before burning?

Solution: Mg forms a thin layer of Mg(OH)₂ or MgO in air. This layer — barrier against Mg burning. Rubbing with sandpaper — removes the layer. Now Mg burns easily.

Q2: Write balanced reactions for:

(a) Sodium with water $$2Na + 2H_2O \rightarrow 2NaOH + H_2\uparrow$$

(b) Calcium with water $$Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2\uparrow$$

(c) Potassium with water $$2K + 2H_2O \rightarrow 2KOH + H_2\uparrow$$

Q3: Why do Cu objects lose their shine after some time?

Solution: Cu + air (CO₂ + O₂ + H₂O): $$2Cu + O_2 + CO_2 + H_2O \rightarrow Cu(OH)_2 \cdot CuCO_3$$ Green patina forms. Cu shine is hidden. By rubbing with 'tamarind juice' — patina dissolves, shine returns.

Q4: Can Fe displace Cu, Cu displace Ag from AgNO₃?

Solution: Series: $Fe > Cu > Ag$

Yes! Both:

• $Fe + CuSO_4 \rightarrow FeSO_4 + Cu$ (Fe > Cu)
• $Cu + 2AgNO_3 \rightarrow Cu(NO_3)_2 + 2Ag$ (Cu > Ag)

Q5: Fe nail + AgNO₃ → ? Reason?

Series: $Fe > Ag$.

Reaction: $$Fe + 2AgNO_3 \rightarrow Fe(NO_3)_2 + 2Ag$$

Observations:

• Colourless AgNO₃ → green Fe(NO₃)₂.
• Shiny Ag layer on Fe nail.

Q6: Identify ionic bonds:

ZnO, K₂SO₄, CO₂, MgCl₂, NH₃

Solution: Metal + Non-metal = Ionic:

• ✓ ZnO (Zn + O)
• ✓ K₂SO₄ (K + SO₄)
• ✗ CO₂ (C + O — both non-metals)
• ✓ MgCl₂ (Mg + Cl)
• ✗ NH₃ (N + H — both non-metals)

Ionic: ZnO, K₂SO₄, MgCl₂. Covalent: CO₂, NH₃.

[NCERT textbook questions]