Transition elements (3d series):
Definition, general characteristics, oxidation states and their stabilities,
The ten elements from Scandium to Zinc form the first transition metal series. They closely resemble each other and are hard, dense, shiny metals with high melting and boiling points.
Common oxidation states are +2 and +3, with the +2 state more common towards the end. The higher oxidation states are shown in compounds with electronegative elements like O, Cl or F (e.g. Cr2O7^2- [+6], MnO4^- [+7]).
Variable oxidation state is found because of the small difference in energy between the 3d and 4s sub-shells. This allows varying numbers of electrons to be used in bonding. When forming ions transition metals lose electrons from the 4s sub-shell before the 3d.