Question

The number of 4f electrons in the ground state electronic configuration of \(Gd^{2+}\) is _________. [Atomic number of Gd = 64] (Integer answer)

Hint:

Gadolinium is a classic example in exams. Remember the "4f7 5d1 6s2" rule for Gd and "4f14 5d1 6s2" for Lu. Electrons are always removed from 6s first.

Answer 1

Correct Answer: 7

The atomic number of Gadolinium (Gd) is 64. To find the number of 4f electrons in the ground state electronic configuration of \(Gd^{2+}\), follow these steps:
1. Determine the electronic configuration of neutral Gd (Z=64): [Xe] 4f⁷ 5d¹ 6s².
2. Remove two electrons to form \(Gd^{2+}\). Electrons are removed from the outermost orbitals, so subtract two 6s electrons:
[Xe] 4f⁷ 5d¹.
3. In the configuration, the 4f subshell holds 7 electrons.
4. Thus, the number of 4f electrons in \(Gd^{2+}\) is 7.
Conclusion: The number of 4f electrons in \(Gd^{2+}\) is 7, fitting within the expected range of 7 to 7.