The difference in the number of unpaired electrons of a metal ion in its high-spin and low-spin octahedral complexes is two. The metal ion is:

Step-by-step solution

The electronic configuration for Co 2 + z = 27 = 4 s 0 3 d 7   When it combines with weak ligands (high spin complex), t 2 g 2 ,2 , 1   eg 1 ,1 , it has 3 unpaired electrons, whereas when it bonds with strong ligands (low spin complex), t 2 g 2 ,2 , 2   eg 1 ,0 , then, it has 1 unpaired electron. The difference in number of unpaired electrons is equal to two.