Question

please tell me how to find or how to calculate the valancy of an element

Answer 1

electronicconfiguration is the method u have to learn

Answer 2

The valency of an atom is equal to the number of electrons in the outer shell if that number is four or less. Otherwise, the valency is equal to eight minus the number of electrons in the outer shell. Once you know the number of electrons, you can easily calculate the valency.