How do i find the valence electron for Chlorine.

You look at which column it's in (seventh). that means its outer shell has 7 valence electrons

And 7 electrons in the outer shell means it lacks 1 to make an octet; therefore, it will gain 1 electron to make the valence of Cl -1.

Generally, Group I elements have 1 electron in their outer shell; they lose this one to become a +1 valence.
Group 2 elements have 2 electrons in their outer shell; they lose these two to have a valence of +2.
Group 3 works the same way for +3.
Group 17 elements (or group VIIA depending upon the system you are using) have 7 electons in the outer shell; they gain one electrons for a valence of -1.
Group 16 elements (or VIA) have 6 e in their outer shell and they gain 2 electrons for a valence of -2.
Group 15 elements (or VA) have 5 e in their outer shell; they want to gain 3 electrons for a valence of -3.

To find the number of valence electrons for an atom of chlorine, you can refer to its position on the periodic table.

First, locate chlorine on the periodic table. Chlorine (Cl) is in Group 17, which is also known as Group 7A or the halogens.

Group 17 elements have a general valence electron configuration of ns²np⁵, where n represents the principal energy level. Since chlorine is in the third period (n = 3), its valence electron configuration is 3s²3p⁵.

To calculate the number of valence electrons, we add the number of electrons in the 3s and 3p orbitals:
2 (from the 3s orbital) + 5 (from the 3p orbital) = 7

Therefore, an atom of chlorine has 7 valence electrons.