What is the valency of chlorine?

 1

Chlorine's atomic number is 17, and its electronic configuration is 2, 8, 7.

The outermost shell has 7 electrons, meaning it needs 1 more electron to complete its octet (8 electrons for stability).

Valency is determined by the number of electrons an atom needs to gain, lose, or share to achieve a stable configuration.

Since chlorine needs 1 electron, its valency is 1.