Question

Explain why elements in group i and vii of the periodic table have the same valancey

Answer 1

Answer:

The valency of an element is determined by the number of valence electron in the outermost shell of an atom of an element. ... Therefore, elements in the same group should have the same valency. For example, the elements of group I contain only one valence electron, the valency of elements of group I is one.

Answer 2

valency can be described as the outer most electrons of the atom

or valency can be described as octet (8) minusouter most electrons

so I and vii has same valency