How many valence electrons does a Cl atom have?

[Caiter2013]

The electron configuration for chlorine, Cl is [Ne]3s23p5. How many valence electrons does a Cl atom have?
Write the symbol for the ion it forms to achieve a noble-gas configuration.

[penza]

If you count from left to right on the periodic table, Cl is in the 7th group, so 7 valence electrons.

It would achieve Argon electron configuration by gaining an electron.

1s2, 2s2, 2p6, 3s2, 3p6, which is the configuration of Argon.

Oh - and the ion it forms would be Cl-

hope that helps!

[mydiamond]

Chlorine comes under group 17. Therefore, it has 7 unpaired valence electrons.

http://macro.lsu.edu/russo/Courses/1201WebS99/pictures/LewisCl.gif  - This image shows you the no. of valence electrons.

As it has 7 unpaired electrons, it needs just one more to complete its octet in order to attain stable noble gas configuration (of Argon).
Here is the diagram of chloride ion: http://www.green-planet-solar-energy.com/images/chloride-ion.gif

Symbol : Cl^-