After recharging a nickel-cadmium cell, what is the oxidation state of nickel?

When a nickel-cadmium (NiCd) cell is recharged, the nickel in the cell undergoes oxidation and its oxidation state is vital to understand its chemical behavior in the cell. In a typical nickel-cadmium battery, nickel is in the form of nickel hydroxide (Ni(OH)2) during discharge, where it has an oxidation state of +2.

During the recharging process, this nickel hydroxide is oxidized to nickel oxyhydroxide (NiO(OH)), which has a higher oxidation state. In this oxidized form, nickel is typically found in the +3 oxidation state. This transition reflects the transfer of electrons during the charging process, where nickel is going from a lower oxidation state (+2) to a higher oxidation state (+3).

Thus, the oxidation state of nickel after the cell has been recharged is +3, making this the correct choice. Understanding the electrochemical reactions occurring in nickel-cadmium cells is crucial for predicting the oxidation states of the materials involved.