The electronic configuration having maximum difference in first and second ionization energies is:
A.\[1{s^2}2{s^2}2{p^6}3{s^2}\]
B.\[1{s^2}2{s^2}2{p^6}3{s^2}3{p^1}\]
C.\[1{s^2}2{s^2}2{p^6}3{s^2}3{p^2}\]
D.\[1{s^2}2{s^2}2{p^6}3{s^1}\]

Hint:To answer this question, you should recall the concept of electron configuration. The electron configuration of an element describes how electrons are distributed in its atomic orbitals. Electron configurations of atoms follow a standard notation in which all electron-containing atomic subshells.

Complete Answer:
 The electronic configuration of elements is based on majorly 3 rules:
According to the Pauli exclusion principle in an atom, no two electrons will have an identical set or the same quantum numbers. There salient rules of Pauli Exclusion Principle are that only two electrons can occupy the same orbital and the two electrons that are present in the same orbital should be having opposite spins.
According to Hund’s Rule of Maximum Multiplicity rule for a given electronic configuration of an atom, the electron with maximum multiplicity falls lowest in energy.
According to the Aufbau principle, the electrons will start occupying the orbitals with lower energies before occupying higher energy orbitals.
Consider the configurations of the options after the loss of an electron: -
\[A.\,1{s^2}2{s^2}2{p^6}\,\& B.\,1{s^2}2{s^2}2{p^6}3{s^1}\,\& \,C.1{s^2}2{s^2}\,\& \,1{s^2}2{s^2},2{p^6},3{s^2},3{p^2}\].
The difference between IE1​ and IE2​ will be maximum for the case where there is a fully filled orbital. In this case, option A has attained noble gas configuration after the loss of an electron.
Hence, option A has the maximum difference between IE1​ and IE2​.

Hence, the correct option is option A.

Note:
The main reason for filling of the electron in \[\;3d\] orbital rather than \[4s\] is due to increased stability of half-filled and fully orbitals are:
Symmetrical distribution: Nature loves symmetry as it leads to increased stability and less energy
Exchange energy: The electrons when present in their degenerate orbitals i.e. orbitals with the same energy with parallel spin have shown to exchange their position. The energy released by these exchanges is known as exchange energy. More the exchange of energy and more stability.