Q.

Consider the transition metal ions Mn3+, Cr3+, Fe3+ and Co3+ and all form low spin octahedral complexes.  The correct decreasing order of unpaired electrons in their respective d-orbitals of the complexes is                [2026]

1 Cr3+>Mn3+>Fe3+>Co3+  
2 Mn3+>Fe3+>Co3+>Cr3+  
3 Fe3+>Co3+>Mn3+>Cr3+  
4 Cr3+>Fe3+>Co3+>Mn3+  

Ans.

(1)

Co3+→3d6⇒t2g2,2,2 eg0,0,   unpaired electron=0

Fe3+→3d5⇒t2g2,2,1 eg0,0,   unpaired electron=1

Cr3+→3d3⇒t2g1,1,1 eg0,0,   unpaired electron=3

Mn3+→3d4⇒t2g2,1,1 eg0,0,   unpaired electron=2