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Question
Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?
Solution
Transition elements have an incomplete set of d-orbitals in their penultimate shell. They have their valence electrons in (n−1)d- and ns-orbitals. Since there is very little energy difference between these orbitals, electrons from both the energy levels can be used for bond formation. As a result, transition elements exhibit variable oxidation states.
Valence shell electronic configuration for Mn (Z = 25): 3d5 4s2
In the 3d series, Mn has the maximum number of unpaired electrons present in the d-subshell (5 electrons). Hence, Mn exhibits the maximum number of oxidation states, ranging from +2 to +7.
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