Question

why Fe does not have +5 oxidation state

Answer 1

Dear Student,

Valence shell electronic configuration of Fe=3d⁶ 4s^​2
After losing 5 electrons, i.e. for Fe⁵⁺ the configuration becomes 3d³ which is unstable. Generally, Fe exist as Fe²⁺ (3d⁶) and Fe³⁺(3d⁵). Out of these two, Fe³⁺ is more stable as here the d shell is half filled.