P-Block Elements

1) Position in Periodic Table

• P-Block elements belong to Groups 13 to 18
• General electronic configuration: ns² np¹–⁶
• Includes metals, metalloids and non-metals

2) General Trends in P-Block

• Atomic radius decreases across a period
• Ionisation enthalpy increases across a period
• Electronegativity increases from left to right
• Metallic character decreases across a period

3) Oxidation States

• Shows variable oxidation states
• Maximum oxidation state = group number
• Lower oxidation states become more stable down the group due to inert pair effect

4) Inert Pair Effect

• Reluctance of ns² electrons to participate in bonding
• More prominent in heavier elements (Tl, Pb, Bi)
• Caused due to poor shielding by d and f orbitals

5) Group-wise Highlights

Group 13 – Boron Family

• Boron is a metalloid; others are metals
• Common oxidation state: +3
• AlCl₃ exists as dimer (Al₂Cl₆)

Group 14 – Carbon Family

• Oxidation states: +4 and +2
• Carbon shows catenation and allotropy
• Pb²⁺ more stable than Pb⁴⁺ due to inert pair effect

Group 15 – Nitrogen Family

• Oxidation states range from −3 to +5
• NH₃ shows hydrogen bonding
• N₂ has strong triple bond

Group 16 – Oxygen Family

• Oxidation states: −2, +2, +4, +6
• Oxygen shows hydrogen bonding
• Ozone (O₃) is a powerful oxidising agent

Group 17 – Halogens

• Highly electronegative non-metals
• Oxidation states: −1 to +7 (except F)
• Reactivity decreases down the group

Group 18 – Noble Gases

• Valence shell completely filled
• Xe forms compounds like XeF₂, XeF₄, XeF₆
• Low boiling points

6) Important Compounds

Ammonia (NH₃)

N₂ + 3H₂ → 2NH₃

• Trigonal pyramidal shape
• Shows hydrogen bonding

Sulphuric Acid (H₂SO₄)

• Strong dibasic acid
• Powerful dehydrating agent

Hydrogen Halides (HX)

• Acidic strength: HF < HCl < HBr < HI
• HF shows hydrogen bonding

7) Anomalous Behaviour

• First element of each group shows anomalous behaviour
• Due to small size, high electronegativity and absence of d-orbitals