How do transition metals exhibit variable oxidation states?

Transition metals exhibit variable oxidation states due to the presence of unpaired electrons in their d-orbitals.

Transition metals are unique in the periodic table because they have unpaired electrons in their d-orbitals. This is a result of the electron configuration of these elements, where the 4s and 3d sublevels are very close in energy. When a transition metal atom loses electrons, it can lose them from either the 4s or 3d sublevel, leading to a variety of possible oxidation states.

The term 'oxidation state' refers to the degree of oxidation of an atom in a chemical compound. In simpler terms, it is the charge that an atom would have if all bonds were ionic. For transition metals, the oxidation state can vary because they can lose different numbers of electrons from the 4s and 3d sublevels. For example, iron (Fe) can exist in either the +2 or +3 oxidation state, depending on whether it loses two or three electrons.

The ability of transition metals to exist in multiple oxidation states is one of their most important properties. It allows them to form a wide range of different compounds and to act as catalysts in many chemical reactions. For example, the transition metal manganese (Mn) can exist in oxidation states from +2 to +7, allowing it to form a variety of different compounds and to participate in many different chemical reactions.

In summary, the variable oxidation states of transition metals are a result of the unique electron configuration of these elements, with unpaired electrons in their d-orbitals. This allows them to lose different numbers of electrons and to exist in a variety of different oxidation states, leading to a wide range of chemical behaviour.