Ni^{2+ ​} has a lower magnetic moment than Co²⁺. Why?
 

Hi,

Electronic configuration of Ni^​+2 is  [Ar] 4s03d8  


Electronic configuration of Co²⁺ is  [Ar] 4s03d⁷.

Number of unpaired electron in d orbital of Ni⁺² is 2 while in Co ⁺² is 3.

Magnetic moment is given by
 

 where, n is the number of unpaired electrons.

As the number of unpaired electron increases magnetic moment increases so Ni^2+ ​ has a lower magnetic moment than Co²⁺.


Regards