The p-Block Elements

Boric acid contains planar BO₃^3- ions which are linked together through hydrogen bonding shown in the fig.

Excess of CO₂ absorbs heat radiated by the earth. Some of it is dissipated into the atmosphere while the remaining part is radiated back to the earth. As a result, temperature of the earth increases. This is the cause of global warming.

The highly poisonous nature of CO arises because of its ability to form a complex with haemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex. This prevents haemoglobin in the red blood corpuscles from carrying oxygen round the body and ultimately resulting in death.

Since, anhydrous HF is a covalent compound and weak acid due to high bond dissociation energy. AlF₃does not dissolve in HF.
Whereas NaF is ionic compound.
3NaF + AlF₃ → Na₃ [AlF₆]
Na₃ [AlF₆] + 3BF₃ (g)→ AlF₃ + 3Na+ [BF]^–

B-Cl bond has dipole moment because of polarity. In BCl_3,  since the molecule is symmetrical (planar), the polarities cancel out and hence the dipole moment is zero

The difference in bond length is due to the difference in the state of hybridisation. In BF₃ 'B' is sp² hybridised and in BF₄^– 'B' is sp³ hybridised.

• PbCl₂ + Cl₂→ PbCl₄.
  This is because Pb can show +2 oxidation state more easily than +4 due to inert pair effect.
• PbCl₄→ PbCl₂ + Cl₂
  Because Pb²⁺ is more stable than Pb⁴⁺ due to inert pair effect.
• PbI₄does not exist because I^- ion being a powerful reducing agent reduces Pb⁴⁺ ion to Pb²⁺ ion in solution.

Pb⁴⁺ + 2I^– → Pb²⁺ + I₂

(a) CO₃^2-  (sp²) (b) Diamond (sp³) (c) Graphite (sp²)