Question

which having maximum no of unpaired electrons .
1.cu+2
2.ni+3
3.fe+3
4. zn

Answer 1

Electronic configurations :
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=> Cu = [Ar] 3d10 + 4s1

So, Cu 3+ = [Ar] 3d9

=> Ni = [Ar] 3d8 + 4s2

So, Ni 3+ = [Ar] 3d7

=> Fe = [Ar] 3d6 + 4s2

So, Fe 3 + = [Ar] 3d5

=> Zn = [Ar] 3d10 + 4s2

Now,
The maximum unpaired electrons in d orbital can be only 5

And Fe3+ has 5 electrons in d orbital.

Rather

Cu 2+ has only 1 and Ni3+ has 3 unpaired electrons.

Whereas Zn has fully filled orbital and no unpaired electrons.

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Thus Fe3+ has maximum unpaired electrons.

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Answer 2

The third one which is Fe3+