Question

Why octahedral complesxes of ni2+ must be outer electron complexe?

Answer 1

Since the coordination number of Ni in the complex is 4, the configuration of Ni+2 , at first sight, shows that the complex is formed by sp 3 hybridization and it is paramagnetic and it has two unpaired electrons. However, experiments show that the complex is diamagnetic, i.e. it do not have unpaired electrons, this is possible when 3d electrons rearrange against the hund’s rule as shown in the below configuration.