# Why do transition metals have variable oxidation states?

Jan 15, 2018

Well, they have many orbitals of similar energy... so they can use them.

The possible oxidation states have already been shown here.

The d-block transition metals often use $d$ and $s$ orbitals to bond... such as in $\pi$ back-bonding shown here...

...and the f-block transition metals often use $f$, $d$, and $s$ orbitals to bond...

[This is the uranium complex known as tris(cyclopentadienyl)tert-butylisocyanouranium(III).]

Hence, the large pool of valence orbitals allow a flexible selection of oxidation states.