Question

In solid state, $PC{l}_5$ is a:

• A. Ionic solid with $[PC{l}_4{]}^{+}$ tetrahedral and $[PC{l}_6{]}^{-}$
  octahedral
  
• B. Ionic solid with $[PC{l}_6{]}^{+}$ octahedral and $[PC{l}_4{]}^{-}$ tertrahedral
  
  
• C. Covalent solid
• D. Octahedral structure

Answer 1

The correct option is A Ionic solid with $[PC{l}_4{]}^{+}$ tetrahedral and $[PC{l}_6{]}^{-}$

octahedral

$PC{l}_5$ in gaseous and liquid state has trigonal bipyramidal geometry due to $s{p}^{3}d$ hybridisation. This is in accordance with the VSEPR theory.

However, in the solid-state, $PC{l}_5$ exists as ionic pairs of and $PC{l}_6^{-}$ by combining two molecules of $PC{l}_5.$ This is because ionic bonding strengthens the structure of the crystal.

$PC{l}_4^{+}$ has $s{p}^3$ hybridisation and tetrahedral geometry.

$PC{l}_6^{-}$ has $s{p}^3{d}^2$ hybridisation and octahedral geometry.

Both these ionic structures fit well into each other giving a solid structure and are more stable.

So, option (D) is the correct answer.