Question

The electronic configuration of chlorine atom is:
(A) $1{s^2}2{s^2}{p^6}3{s^3}{p^5}$
(B) $1{s^2}2{s^2}{p^6}3{s^3}{p^4}$
(C) $1{s^2}2{s^2}{p^6}3{s^2}{p^5}$
(D) $1{s^2}2{s^2}{p^6}3{s^2}{p^6}$

Answer 1

Chlorine is a non-metal which lies in the group $17$ of the periodic table. To write the electronic configuration of chlorine we need the atomic number of chlorine i.e. the number of protons that are present in the nucleus of the atom.

Complete step by step solution:
Electron Configurations are very useful for calculating the valency of a particular atom. It also helps in predicting the properties of a group of elements as those elements that have alike electronic configuration shows similar properties. You can also interpret the atomic spectra with the help of atomic configuration. The notation used for the writing E.C. of electrons in the atomic orbitals of atoms came into existence shortly after Neil Bohr’s model of the atom in $1913$ .
The $(n + l)$ rule governs the order in which electrons are filled in orbitals in the successive atoms of the periodic table. Electrons are filled in increasing order of the energy of orbitals, from lowest energy orbital to highest energy orbital. The energy of electrons increases as their $(n + l)$ values increase. According to the Aufbau principle, In the ground state of atom electrons are filled in the increasing order of their energies. $$ 1s < 2s < 2p < 3s < 3p $$ which is in the order of increasing $(n + l)$ . Hence, electrons will first be filled in $1s$ orbital and then $2s$ , $2p$ , $3s$ and $3p$ . The atomic number of chlorine is $17$ . It means $17$ electrons revolve around the nucleus in its shell. The filling of electrons will take place according to the Aufbau principle. Hence, its electronic configuration will be $1{s^2}2{s^2}{p^6}3{s^2}{p^5}$ .
Therefore, option (C) is correct.

Note:
The electron configuration of an element is written to explain how the electrons are distributed in the respective atomic orbitals. It is written by following a standard notation in which all electron-containing atomic subshells are put in a fixed sequence.