Give the significance of `d^4` ions in octahedral field.

Explanation

(i) If `Delta_0 lt P`, the `4^(th)` electron enters into one of the `e_g` orbitals giving the configuration `t_2^3 e_g^1` . Ligands from which `Delta_0 lt P` are called weak field ligands. So they form high spin complexes.
(ii) If `Delta_0 gt P`, the `4^(th)` electron enters into `t_(2g)` orbitals giving the configuration `t_(2g)^4 e_g^0`. Ligands which produce this effect are called strong field ligands. So they form low spin complexes.