Write down the number of 3d electrons in each of the following ions : `Ti^(2+), V^(2+), Cr^(3+), Mn^(2+), Fe^(2+), Fe^(3+), Co^(2+), Ni^(2+)` and `Cu^(2+)`. Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

Explanation

In an octahedral field, d - orbitals undergo crystal field splitting into two sets : `t_(2g)` set `(d_(xy), d_(yz), d_(zx))` having lower energy and `e_(g)` set `(d_(x^(2)-y^(2)), d_(z^(2)))` having higher energy. Since `H_(2)O` is a weak ligand, the difference in energy between `t_(2g)` and `e_(g)` orbitals is small. Hence, the electronic arrangement in the d - orbitals of the metal in aqua complexes will be as follows :