What is the electron configuration for a chloride ion?

##1"s"^2 2"s"^2 2"p"^6 3"s"^2 3"p"^6##

OR

##"[Ne]" 3"s"^2 3"p"^6##

The of a chlorine atom (##"Cl"##) is as follows:

##1"s"^2 2"s"^2 2"p"^6 3"s"^2 3"p"^5##

But a chlorine ion (##"Cl"^-##) has acquired a ##"(1)-"## charge as a result of gaining 1 electron. Thus, its electron configuration is:

##1"s"^2 2"s"^2 2"p"^6 3"s"^2 3"p"^6##

This may also be expressed as:

##"[Ne]" 3"s"^2 3"p"^6##