Question

define the term valency how is it different from valance electrons find the valancey of oxygen and fluorine

Answer 1

Valence electrons are the electrons in the outer most shell. Valency is same as valence electrons but if valence electrons are more than 4 then you have to subtract it from 8 to get valency.

Answer 2

valency means the combining capacity of the elements or valency is the no. of electron which can take part in the chemical reaction
valence electrons means the electrons present in the valence shell or outermost orbit of an electron
valency of oxygen is 2 and that of fluorine is 1