| The d-electron configurations of Cr2+, Mn2+, Fe2+ and Ni2+ are 3d4, 3d5, 3d6 and 3d8 respectively. Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour? [AIPMT (S) 2007] |
| (At. no. Cr = 24, Mn = 25, Fe = 26, Ni = 28) |
A) [Mn(H2O)6]2+
B) [Fe(H2O)6]2+
C) [Ni(H2O)6]2+
D) [Cr(H2O)6]2+
Correct Answer: C
Solution :
| [c] As the number of unpaired electron increases, the magnetic moment increases and hence the paramagnetic behaviour increases. |
| So, Cr2+ (22) = 3d4 - 4 unpaired electrons |
| Mn2+ (23) = 3d5 - 5 unpaired electrons |
| Fe2+ (24) = 3d6 - 4 unpaired electrons |
| Ni2+(26) = 3d8 - 2 unpaired electrons |
| So, [Ni(H2O)6]2+ exhibit minimum paramagnetic behaviour. |
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