NEETChemistryd and f Block Elements
Which of the following pairs of ions possesses the exact same number of unpaired electrons?
Options
- AMn ²⁺ (Z = 25) and Sm ³⁺ (Z = 62)
- BFe ²⁺ (Z = 26) and Gd ³⁺ (Z = 64)
- CNi ²⁺ (Z = 28) and Ce ³⁺ (Z = 58)
- DV ³⁺ (Z = 23) and Nd ³⁺ (Z = 60)
Correct answer
A. Mn ²⁺ (Z = 25) and Sm ³⁺ (Z = 62)
Step-by-step solution
The number of unpaired electrons is determined by writing the electronic configuration of each ion. For Mn ²⁺ (Z = 25): The neutral atom is [ Ar ] 3 d ⁵ 4 s ² . Removing two electrons from the 4s orbital gives [ Ar ] 3 d ⁵ , which has 5 unpaired electrons. For Sm ³⁺ (Z = 62): The neutral atom is [ Xe ] 4 f ⁶ 6 s ² . Removing three electrons (two from 6s, one from 4f) gives [ Xe ] 4 f ⁵ , which has 5 unpaired electrons. Both Mn ²⁺ and Sm ³⁺ have 5 unpaired electrons. Evaluating the other options: Fe ²⁺ has 4 unpaire