This group of metals are distinguished from other metals not by their physical properties, but by their electronic structure. The transition metals have their valence electrons in more than one shell. Regular, or representative, metals have their valence electrons in only one shell.

The transition metals include the elements of the groups IIIB through IB in each of the long periods of the periodic table.

The transition metals are noted for their variability in oxidation state. This is attributed to the presence of valence electrons in more than one shell. Whereas, the representative metals have only one or two oxidation states, since they have valence electrons in only one shell.

Thus, manganese has two electrons in its outside shell and five electrons in the next shell down, and exhibits oxidation states of +1, +2, +3, +4, +5, +6, and +7.

They are also characterized by the fact that well into the series, going from left to right, the properties of succeeding metals do not differ greatly from preceding ones. This is attributed to the fact that, generally, succeeding elements differ in electronic structure by one electron in the next to the outer valence shell rather than the outer shell.

In contrast, those of succeeding representative metals in a period differ extensively, since they differ by one electron in the outer valence shell.