Which transition element does not exhibit variable oxidation states?

Transition Elements

• The elements in the D block are those that can be found in the periodic table from the $3$ to the $12$ groups.
• Transition elements or transition metals are other names for D block elements.

Scandium$\left(\mathrm{Sc}\right)$

• All D-block elements have different valencies or different oxidation numbers.
• Scandium $(Z=21)$ does not exhibit variable oxidation states.
• The oxidation state exhibited by scandium is $+3$.
• For scandium, the number of electrons in the 3d and 4s orbitals is $1$ and $2$ respectively.