Why is the oxidation state of +2 common among transition metals?

The oxidation state of +2 is common among transition metals due to the ease of losing two 4s electrons.

Transition metals are elements found in groups 3-12 of the periodic table. They are characterised by their ability to form stable ions with different oxidation states. The oxidation state of an atom is a measure of the degree of oxidation of an atom, defined as the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic.

The most common oxidation state among transition metals is +2. This is primarily because transition metals have two 4s electrons that are relatively easy to remove. The 4s orbital is filled before the 3d orbital when adding electrons to these atoms, but it is also emptied before the 3d orbital when these atoms are ionised. This is due to the fact that the 4s electrons are further from the nucleus and are therefore held less tightly. As a result, it is energetically favourable for transition metals to lose these two 4s electrons and form a +2 ion.

Furthermore, the loss of two electrons to form a +2 ion results in a stable electron configuration. For many transition metals, the +2 oxidation state corresponds to a completely filled or half-filled d subshell, which is particularly stable due to electron-electron interactions. This stability further encourages the formation of +2 ions.

In addition, the +2 oxidation state allows transition metals to form a variety of complex ions and coordination compounds. These compounds often have interesting properties and are important in many areas of chemistry, including catalysis and biochemistry. The versatility of the +2 oxidation state contributes to its prevalence among transition metals.

In conclusion, the +2 oxidation state is common among transition metals due to the ease of losing two 4s electrons, the stability of the resulting electron configuration, and the ability to form a variety of complex ions and coordination compounds.