How many valence electrons are in an atom of chlorine?

Chlorine has 7 valence electrons .

The of chlorine is ##1s^2 2s^2 2p^6 3s^2 3p^5## or ##"[Ne]"3s^2 3p^5##.

The ##3s^2 3p^5## electrons are the outermost electrons, so chlorine has seven .

In a picture, the valence electrons are the ones in the outermost shell.

You can see in the diagram below that there are seven electrons in the outermost circle.

Additionally, a more basic way of determining the number of would be to simply look at what group Cl is in.

It is in Group 17, which means it has 7 valence electrons.