Question

Explain inadequacies octet rule with respect to

1. Incomplete octet
2. Expanded octet

Answer 1

1. Incomplete octet:
   e.g. BF₃, BeCl₂, LiCl
   In these covalent molecules, the atoms B, Be, and Li have less than eight electrons in their valence shell but these molecules are stable.
   Li in LiCl has only two electrons, Be in BeCl₂ has four electrons while B in BF₃ has six electrons in the valence shell.
   
2. Expanded octet: 
   Some molecules like SF₆, PCl₅, H₂SO₄ have more than eight electrons around the central atom.
   
   SF₆; 12 electrons around sulfur
   
   PCl₅; 10 electrons around Phosphorus
   
   H₂SO₄; 12 electrons around sulfur