3d series elements exhibit variable oxidation states because the energies of their ns and (n-1)d orbitals are similar, allowing electrons from both orbitals to participate in bond formation. Here are some other details about the oxidation states of 3d series elements:
Scandium: The first transition metal, scandium, has a +3 oxidation state.
Stability: The +3 oxidation state is stable at the beginning of the 3d series, but the +2 oxidation state becomes more stable towards the end.
Lowest oxidation state: The lowest oxidation state corresponds to the number of ns orbital electrons.
Most common oxidation state: For the first-row transition elements, the most common oxidation state is +2, except for scandium.
Reason for +2 oxidation state: The +2 oxidation state is due to the loss of two 4s-electrons.
