Why is zinc not considered a typical transition metal?

Zinc is not considered a typical transition metal because it does not form ions with incomplete d-orbitals.

Zinc is located in the d-block of the periodic table, which is typically associated with transition metals. However, it is not considered a typical transition metal due to its electron configuration and the nature of its ions. The defining characteristic of transition metals is their ability to form ions with incomplete d-orbitals. This property allows them to exhibit variable oxidation states, form coloured compounds, and act as catalysts in various chemical reactions.

Zinc, however, does not exhibit these properties. Its electron configuration is [Ar] 3d10 4s2. When it forms ions, it loses the two 4s electrons to become Zn2+ with the electron configuration [Ar] 3d10. This means that zinc ions have a completely filled 3d-orbital, not an incomplete one. Therefore, zinc does not exhibit variable oxidation states. It only forms +2 ions, unlike other transition metals which can form a variety of positive ions.

Furthermore, compounds of zinc are not coloured. This is because the d-orbitals are fully occupied and there are no d-d transitions possible that can absorb visible light and result in coloured compounds. This is in contrast to other transition metals which form coloured compounds due to d-d transitions.

Zinc also does not act as a catalyst in the same way as other transition metals. While it can participate in some catalytic reactions, it does not do so by providing a surface for reactions to occur on, as is typical of transition metals. Instead, it often acts as a structural component in enzymes, facilitating reactions in that way.

In summary, while zinc is located in the d-block of the periodic table, it does not exhibit the typical properties of transition metals such as forming ions with incomplete d-orbitals, exhibiting variable oxidation states, forming coloured compounds, and acting as a catalyst in chemical reactions. Therefore, it is not considered a typical transition metal.