Some important conclusions regarding oxidation States of transition metal
The variable oxidation states of transition metals are due to participation of inner (n-1)d and Outer ns electrons.
Except scandium the most common Oxidation state of the first transition metals is +2 which arises due to loss of 2 4s electrons.
The elements which show greatest number of oxidation States occur in or near the middle of the series example in first transition series
Eg. Manganese exhibits all the oxidation state from +2 to +7.
The small number of oxidation States at the extreme end of the left hand side is due to a lesser number of electrons to lose or share. On the other and at the extreme right and side is due to the large number of D electrons.
The minimum Oxidation state is equal to the number of electrons in the S orbital and Highest Oxidation state is equal to the sum of outer S and some or all d electrons.
In the +2 and + 3 Oxidation State the bonds formed are mostly ionic and in compounds of higher oxidation States the bonds are covalent.
Within the group maximum Oxidation State increases with atomic number.
Example iron of group 8 shows common Oxidation state of plus two and + 3 but Ruthenium and Osmium in D group form compounds n + 4 and +6 and +8 oxidation States.
Transition metals also form compounds in low oxidation States such as plus one and zero or negative for complex.
The variability of Oxidation state in transition elements arises because of incomplete filing of d orbitals in such a way that their Oxidation State differs by Unity Such as Vanadium.
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