Final answer:
The oxidation state of the first row transition elements is +2, except for chromium which also has oxidation states of +3, +4, and +6.
Step-by-step explanation:
The oxidation state of the first row transition elements is predominantly +2, with a few exceptions. One notable exception is chromium (Cr). Chromium exhibits multiple oxidation states, with +2, +3, and +6 being the most common. In its compounds, chromium commonly adopts an oxidation state of +3, as seen in compounds like chromium(III) oxide (Cr2O3). The variability in oxidation states of chromium arises from its unique electronic configuration. Chromium has an electron configuration of [Ar] 3d⁵ 4s¹, where the 3d and 4s orbitals are close in energy. In some compounds, chromium undergoes electron configuration changes, resulting in different oxidation states.
In addition to chromium, manganese (Mn) is another exception. While manganese typically exhibits an oxidation state of +2, it can also display oxidation states ranging from +1 to +7. For instance, manganese dioxide (MnO2) highlights manganese in the +4 oxidation state. These exceptions showcase the versatility of first-row transition elements, as their electronic configurations permit a range of oxidation states. The ability to exhibit multiple oxidation states contributes to the diverse chemistry and reactivity observed in these elements.