Question

The general electronic configuration of the transition elements is:
(A) $(n - 1){d^{10}},\left( {n + 1} \right){s^2}$
(B) $(n - 1){d^{1 - 10}},\left( {n + 1} \right){s^{1 - 2}}$
(C) $(n - 1){d^{1 - 10}},n{p^6},n{s^2}$
(D) $(n - 1){d^{1 - 10}},n{s^{1 - 2}}$

Answer 1

We have to know how the electronic configuration of any elements should be written and what should be the difference in the case of transition elements and the block's effect on the electronic configuration.

Complete step-by-step answer
First we start with that how to write the electronic configuration of any element:
We have to know the atomic number of the element and then we have to know the Aufbau’s Principle (Aufbau’s Principle: It states that the orbitals having lower energy will be filled first, then the higher ones) and the half-filled and fully-filled orbitals have the highest stability concept, then the electronic configuration is ready.
The transition elements are ending with $d -$ orbital. So, also known as the $d -$ block elements. It states that in the transition elements the valence electron will be filled in the $d -$ orbital.
Now, moving towards the options keeping Aufbau’s principle and the stability of full-filled and half-filled orbitals in mind:
In the first, the $d$ and $s$ orbital have fixed numbers of electrons that are filled which is not valid for all the transition elements.
Similarly, in the second, the $(n + 1)s$ orbital has higher energy then the $(n - 1)d$ orbitals. So, the filling of the electrons is not possible. Hence, it is not valid for all the transition elements.
Similarly, in the third, the $p$ orbital may also be filled, but $np$ orbital has higher energy then $(n - 1)d$ the orbitals. Hence, it is not valid for all the transition elements.
Similarly, in the last, as the $ns$ orbital has similar energy with the $(n - 1)d$ orbitals, the $(n - 1)d$ electrons may jump to $s$ for higher stability. Hence, it is valid for all the transition elements.
So, from the above discussion, the electronic configuration of the transition elements is $(n - 1){d^{1 - 10}},n{s^{1 - 2}}$ .
Hence, the correct option is (D) $(n - 1){d^{1 - 10}},n{s^{1 - 2}}$ .

Note
While finding the electronic configuration of any element, the group number and the period number is useful and the knowledge of Aufbau’s Principle and the stability of half-filled and full-filled is must for the filling of electrons in the orbitals.