Which of the following statement is incorrect?

${\mathrm{XeF}}_6\left(s\right)$ is found to be ionic solid consisting of  ${\left[{\mathrm{XeF}}_5\right]}^{+}$ and ${\mathrm{F}}^{-}$ ions.

${\mathrm{FeSO}}_4\cdot 7{\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{MgSO}}_4\cdot 7{\mathrm{H}}_2\mathrm{O}$ are isomorphous to each other.

Transition metals may use inner- d-electrons along with the outer electrons for metallic bonding as $(n-1)d$ and $ns$ have nearly same energy. Hence, their melting points are higher.

Chloral hydrate shows intermolecular hydrogen bonding.