It can be observed from the above table that in the starting of 3d transition series elements like Sc, Ti, V, Cr in +2 state are not that stable in their elements in the +3 state.

In the middle Mn²⁺, Fe²⁺, Co²⁺are quite known. In fact, Mn²⁺ and Mn⁷⁺ are most stable states in Mn. Fe²⁺ is less stable when compared to Fe³⁺ which is due to fact that Fe³⁺ is able to loose one electron to acquire d⁵ state which has extra stability. Co²⁺ is less stable as compared to Co³⁺. Ni²⁺ is the most common and stable among its +2, +3, +4 states. Cu²⁺ is more stable and is quite common as compared to Cu⁺. Towards the end, Zn forms only Zn²⁺ which is highly stable as it has 3d¹⁰ state.

Note: As it becomes difficult to remove the third electron from d-orbital, the stability of +2 oxidation state increases from top to bottom.