Question

Explain briefly how +2 oxidation state becomes more and more stable in the first half of first-row transition elements with increasing atomic number.

Answer 1

The sum of IE₁, and IE₂ increases. Thus, the standard reduction potential becomes less and less negative. Therefore, the tendency to form M⁺² ion decreases. The greater stability of +2 state, say for Mn, is due to half-filled (d⁵) configuration and that for Zn is due to completely filled ‘d’ orbitals. That for nickel is due to the highest negative enthalpy of hydration.