Question

What happens when chlorine atom gains an electron in its outer energy shell?

Answer 1

A neutrally charged chlorine atom becomes a negatively charged chlorine ion.

Answer 2

Explanation:

Atomic number of chlorine is 17 and its electronic configuration is as follows.

                  $1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$

Since, to become stable in nature chlorine requires only one electron from a donor atom.

As it is known that species that gain electrons will obtain a negative charge and species that lose electrons will obtain a positive charge.

Hence, when chlorine will gain an electron to become stabilized then it will change into chlorine ion or $Cl^{-}$ ion.