Question

how to find valency of any element only with help of atomic number

Answer 1

If we know the electronic configuration of the element you can find the Valence easily. Exception to this is Transition elements i.e. D-block, they have variable oxidation state so the Valence.

For example: Bromine (35): [Ar]3d10 4s2 4p5

It belongs to halogens it's Valence is -1

Valence electrons are 7.(5+2)

MARK BRAINLIEST....

Answer 2

Use electronic configuration table that is 2 8 8 18 36

Eg hydrogen 1 valency is 1

Atomic no 15. Electronic configuration 2 8 5 for complete 8 we need 3 electrons for becoming stable

So valency is 3

Hope it helps