Question

Amoung the componds, ${PCI}_4^{+}$ and ${PCI}_4^{-}$ ;which one is not likely to exist and why?

Answer 1

The oxidation state of P in $PC{l}_4^{+1}$ is +5 while the oxidation state of P in $PC{l}_4^{-1}$is +3.

As we move down the group, the stability of +5 oxidation state decreases and the stability of +3 oxidation state increases. Chlorine belongs to third period. Hence, $PC{l}_4^{+1}$ compound is more likely to exist.