Manganese, for example,
exhibits all the oxidation states from +2 to +7 The lesser number of
oxidation states at the extreme ends stems from either too few electrons
to lose or share (Sc, Ti) or too many d electrons (hence fewer orbitals
available in which to share electrons with others) for higher valence
(Cu, Zn) Thus, early in the series scandium(II) is virtually unknown
and titanium (IV) is more stable than Ti(III) or Ti(II) At the other end,
the only oxidation state of zinc is +2 (no d electrons are involved)