This lesson focuses on the chemistry of p‑block elements, which include many non-metals, metalloids, and some metals. These elements show diverse properties and play crucial roles in industrial and biological systems.

1. Core Concepts (Short Notes)

9.1 Location & Characteristics of p‑Block Elements

• Found in Groups 13–18 of the periodic table.

• Electron configuration ends in ns² np¹–np⁶.

• Include: Boron family, Carbon family, Nitrogen family, Oxygen family, Halogens, Noble gases.

• Properties vary widely: metallic → semi-metallic → non‑metallic.

  
  

9.2 General Trends in p‑Block

• Metallic character increases down a group.

• Non‑metallic character increases across a period (left → right).

• Ionization energy increases across but decreases down.

• Electronegativity increases across the period.

  
  

9.3 Important p‑Block Elements & Their Chemistry

Group 13 – Boron Family

Examples: B, Al

• Boron: metalloid, forms covalent compounds.

• Aluminium: reactive metal, forms protective oxide layer (Al₂O₃).

• Compounds: borates, alumina, aluminium chloride.

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Group 14 – Carbon Family

Examples: C, Si

• Carbon forms allotropes: diamond, graphite.

• Silicon used in semiconductors.

• Compounds: CO₂, carbonates, silicates.

Group 15 – Nitrogen Family

Examples: N, P

• Nitrogen: inert triple bond (N₂).

• Phosphorus: white, red forms.

• Compounds: NH₃, nitric acid, phosphates.

Group 16 – Oxygen Family

Examples: O, S

• Oxygen supports combustion.

• Sulfur forms S₈ rings.

• Compounds: oxides, sulfates, sulfides.

Group 17 – Halogens

Examples: F₂, Cl₂, Br₂, I₂

• Highly reactive non‑metals.

• Form –1 ions.

• Strong oxidizing agents.

• React with metals → metal halides.

Group 18 – Noble Gases

Examples: He, Ne, Ar

• Monoatomic gases.

• Very low reactivity.

• Uses: airbags, neon signs, helium balloons.

9.4 Oxides of p‑Block Elements

• Range from acidic → amphoteric → basic across the block.

• CO₂ = acidic oxide.

• Al₂O₃ = amphoteric.

• CaO (not p‑block but comparison) = basic.

9.5 Hydrogen Compounds of p‑Block

• H₂O (bent shape), NH₃ (pyramidal), CH₄ (tetrahedral).

• Thermal stability and acidity/basicity vary along the groups.

2. Key Formula Patterns & Reactions to Remember

Halogen Displacement Reaction

More reactive halogen displaces a less reactive one: Cl₂ + 2Br⁻ → 2Cl⁻ + Br₂

Formation of Acids from Non‑Metal Oxides

SO₂ + H₂O → H₂SO₃ CO₂ + H₂O → H₂CO₃

Ammonia Formation (Haber Process)

N₂ + 3H₂ ⇌ 2NH₃

Silicon Dioxide Reaction With Base

SiO₂ + 2NaOH → Na₂SiO₃ + H₂O

3. Tips & Tricks for Exams

• For halogens: reactivity decreases down the group, but melting/boiling points increase.

• Noble gases are inert → used in non‑reactive environments.

• Oxidizing power of halogens: F₂ > Cl₂ > Br₂ > I₂.

• Remember shapes of molecules using VSEPR theory.

• Allotropes (e.g., carbon forms) are frequently tested.

• Compare acidic/basic nature of oxides using periodic trends.

4. Important Points to Remember

• p‑Block elements are extremely diverse—covering metals, non‑metals, and metalloids.

• Reactivity patterns and oxidation states vary widely.

• Many industrially important compounds (acids, fertilizers, gases) come from this block.

• Halogens and noble gases have distinct, easy‑to‑recognize behaviors.

Periodic trends explain reactivity, acidity, and bonding variations.