COMEDK202510 May 2025Evening ShiftChemistryd and f Block ElementsActual
Which is the correct order of increasing number of unpaired electrons in the following ions? A = Cr ²⁺( Z =24) B = Cu ²⁺( Z =29) C = Ni ²⁺( Z =28) D = Fe ³⁺( Z =26)
Options
- AB < C < A < D
- BD < C < A < B
- CC < B < D < A
- DB < C < D < A
Correct answer
A. B < C < A < D
Step-by-step solution
The electronic configuration of the neutral atoms and their respective ions are determined as follows: For Cr ²⁺ ( Z=24 ): The neutral configuration is [Ar] 3d⁵ 4s¹ . Removing two electrons gives [Ar] 3d⁴ . The number of unpaired electrons is 4 . For Cu ²⁺ ( Z=29 ): The neutral configuration is [Ar] 3d¹⁰ 4s¹ . Removing two electrons gives [Ar] 3d⁹ . The number of unpaired electrons is 1 . For Ni ²⁺ ( Z=28 ): The neutral configuration is [Ar] 3d⁸ 4s² . Removing two electrons gives [Ar] 3d⁸ . The number of unpaired e