Question

JEE MAINS CHEMISTRY QUESTION SEPTEMBER 2020

Answer 1

What is the correct electronic configuration and magnetic moment (spin only) for ⁶⁴Gd³⁺ ion.

1. [Xe] 4f^7 , 7.93 BM
2. [Xe] 4f⁶, 6s¹ , 7.93 BM
3. [Xe ] 4f⁵, 6s², 7.92 BM
4. [Xe] 5f^7, 7.93 BM

solution : electronic configuration of gadolinium ( Gd ) is written as [Xe] 4f^7, 6s² , 5d¹ .

but we have given Gd³⁺ ion, so three electrons are removed from outer most shells (5d¹, 6s²).

so electronic configuration of Gd³⁺ is [Xe] 4f^7 ( half filled f orbital)

as Gd³⁺ has seven unpaired electrons so the magnetic moment of it is μ = √{7(7 + 2)} = √72 = 7.93 BM

Therefore the correct answer is option (1) [Xe]4f^7, 7.93 BM