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Number of complexes from the following with even number of unpaired 'd' electrons is ____. [V(H2O)6]3+, [Cr(H2O)6]2+, [Fe(H2O)6]3+, [Ni(H2O)6]2+, [Cu(H2O)6]2+ [Given atomic numbers : V = 23, Cr = 24, Fe = 26, Ni = 28, Cu = 29]

1. (1) 2
2. (2) 4
3. (3) 5
4. (4) 1

Correct answer: (1) 2

Solution

The correct option is right because only [Cr(H2O)6]2+ and [Cu(H2O)6]2+ have an even number of unpaired 'd' electrons, while the others have either an odd number or are fully paired.

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