Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?
(a) Co2+(b) Cr2+(c) Mn2+(d) Cr3+

Choose the correct option
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)

Electronic configuration of    Co2+ = (Ar) 3d7  ; Number of unpaired electrons = 3
Electronic configuration of  Cr2+ = (Ar) 3d4  ; Number of unpaired electrons = 4
Electronic configuration of    Mn2+ = (Ar) 3d5   ; Number of unpaired electrons = 5
Electronic configuration of   Cr3+ = (Ar) 3d3  ; Number of unpaired electrons = 3
 
Hence, it is clearly seen that both   have same number of unpaired electrons, i.e, 3.