Question

Why do some transition metals have multiple oxidation states?

Answer 1

Answer: The reason is the number of degenerate electrons.

Explanation:  Transition elements are the only elements in the periodic table which are capable of showing variable oxidation states.

Tranistion elements has 'd orbitals' as their penultimate shells which are not perfectly shielded by the inner orbitals. And these d orbitals can occupy 10 electrons in their 5 orbitals.

Thus they can easily lose electrons as the energy of the electrons are the similar or better say that they are degenerate.

Answer 2

Transition metals can have multiple oxidation states because of their electrons. The transition metals have several electrons with similar energies, so one or all of them can be removed, depending the circumstances. ... When they attach to other atoms, some of their electrons change energy levels.