Question

What is the electron configuration of ${\mathrm{Cl}}^{-}$?

Answer 1

Chlorine(Cl):

• Chlorine is a p-block element having atomic number 17.
• Chlorine belongs to group 17 which is known as halogens.

Electronic configuration of Group 17

• The elements of group 17 have seven electrons in their outermost shell.
• So, the valence shell electronic configuration of group 17 is $\text{n}{\mathrm{s}}^2\text{n}{\mathrm{p}}^5$.

Electronic configuration of ${\mathrm{Cl}}^{-}$

• The electronic configuration of fluorine is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^5$.
• ${\mathrm{Cl}}^{-}$ is formed by gaining one electron by chlorine atom.
• So, the electronic configuration of ${\mathrm{Cl}}^{-}$ is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^6$.