Question

Which of the following compounds will exist in ionic form in its solid state?
$N_2{O}_5,PC{l}_5,PB{r}_5,P{F}_5,I{F}_5,I_{2}C{l}_6,N{O}_2$

Answer 1

Compounds that exist as ionic solids are:
$N_2{O}_5\to N{O}_2^{+}+N{O}_3^{-}$
$PC{l}_5\to PC{l}_4^{+}+PC{l}_6^{-}$
$PB{r}_5\to PB{r}_4^{+}+B{r}^{-}$
$I{F}_5\to I{F}_4^{-}+I{F}_6^{-}$
$I_{2}C{l}_6\to IC{l}_2^{+}+IC{l}_4^{-}$

$P{F}_5$ due to the small size and high charge density of $F^{-}$, has more polarisation and hence has more covalent character.