The Nobel gas configuration of the chlorine gas is; [Ne] 3s² 3p⁵.
Chlorine gains one electron to form a noble gas structure. Chlorine contains seven electrons in its outer shell and an atomic number of 17. It achieves a stable electron configuration similar to that of the noble gas argon, which is found in the same era, by accepting an extra electron.
The octet rule is satisfied since this produces a complete outer shell. Therefore, chlorine has the noble gas configuration 2-8-7, which denotes that it has two electrons in the first shell, eight in the second, and an additional electron in the third shell, which achieves stability.