Question

why iron cannot show +5 oxidation state​

Answer 1

Answer:

Fe[V] compounds have been made; in aqueous media they disproportionate into Fe[III] and Fe[VI].

Answer 2

Answer:

If it shows +5 oxidation state , then. it's configuration will be :

$fe - > (ar)3 {d}^{2} 4 {s}^{0}$

which is a highly unstable state because the inner p and s orbitals will do effective shielding and the outermost 3d electrons will be held attracted by nucleus very loosely .

Hence , Fe don't prefer to show +5 Oxidation state