Question

Why does iron only have $2+$ and $3+$ oxidation states?

Answer 1

Both $Fe\left(II\right)$ and $Fe\left(III\right)$ are common oxidation states of iron. They are not the ONLY oxidation states exhibited by iron metal.

Explanation:

The electronic structure of the iron atom predisposes the stability of $F{e}^{2+}$ and $F{e}^{3+}$. Other oxidation states are viable.

Ground state: [Ar] $4s^2,3d^6$

+2 ion: [Ar] $3d^6$

+3 ion: [Ar] $3d^5$