Question

Which metal exhibits more than one oxidation states in their compounds.

• A. $Na$
• B. $Mg$
• C. $Al$
• D. $Fe$

Answer 1

The correct option is D $Fe$

Transition elements show variable state oxidation in their compounds because there is a very small energy difference in between $(n-1)d$ and $ns$ orbitals. As a result, electrons of $(n-1)d$ orbitals as well as $ns$-orbitals take part in bond formation.
Iron $\left(Fe\right)$ being a transition metal has variable oxidation states.