Question

What is the electronic configuration of `"Cl"^(-)`?

Answer 1

`1s^2 2s^2 2p^6 3s^2 3p^6`

Explanation:

We know that the atomic number for `Cl` is 17, `(Z = 17` number of protons). `Cl` have an electron configuration of:

`1s^2 2s^2 2p^6 3s^2 3p^5 -> 2+2+6+2+5 = 17`

Since you wanted the electron configuration of `Cl^-` this would result in an extra electron.
We know that a atom has equal parts of protons and electrons in its ground state.
So when `Cl` becomes `Cl^-` it becomes `Z=18`.

`1s^2 2s^2 2p^6 3s^2 3p^6 -> 2+2+6+2+2+6 = 18`

So that would be the correct electron configuration for `Cl^-`