Question

Gadolinium belongs to 4f series. Its atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
A. $\left[ {Xe} \right]4{f^7}5{d^1}6{s^2}$
B. $\left[ {Xe} \right]4{f^6}5{d^2}6{s^2}$
C. $\left[ {Xe} \right]4{f^8}6{d^2}$
D. $\left[ {Xe} \right]4{f^9}5{s^1}$

Answer 1

Hint – While finding the electronic configuration of any element, always keep in mind that electrons arrange themselves in a way that gains them maximum stability. Half-filled and completely filled orbitals are more stable than randomly filled orbitals.

Complete step-by-step answer:
An atom's electronic configuration is defined as the numeric representation of its electron orbitals. The electronic configuration helps us find how many electron orbitals an atom has and also the number of electrons populating each of its orbitals.
Now let us see step by step how to find the electronic configuration of gadolinium:
The atomic number of Xenon(Xe) is 54, so [Xe] represents a total of 54 electrons. As it is given in the question itself that the atomic number of gadolinium is 64 therefore the total number of electrons to be arranged is: 64-54=10.
As mentioned earlier, electrons arrange themselves in a way that provides them maximum stability.
Since the s-orbital can accommodate 2 electrons, and the f-orbital can accommodate a maximum of 14 electrons, thus the arrangement of 7 electrons in the f-orbital makes it half-filled i.e. more stable. The remaining 1 electron is filled in the d-orbit.
Thus the remaining 10 electrons in order to gain maximum stability arrange themselves in the electronic configuration of : $4{f^7}5{d^1}6{s^2}$
So, the electronic configuration of Gadolinium is: $\left[ {Xe} \right]4{f^7}5{d^1}6{s^2}$
Thus option B is the correct one.

Note – The electron configuration of an element is unique to its position in the periodic table. The energy level is determined by the period and the number of electrons is given by the atomic number of the element. Orbitals that are in different energy levels are identical to each other, but they occupy different areas in space.