Question

The valency of both sodium and chlorine is 1, why?

Answer 1

Because both element shares their one electron to complete its octet.

That's why valency of both elements is same.

Answer 2

Answer:

Sodium is more electropositive due to its small ionisation energy. Hence it is strongly metallic. Chlorine has highest electron affinity and also more electronegativity. So it is more non-metallic.