Question

define a)valency b)atomic size

Answer 1

The combining capacity of a element is its valency. It is determined by no.of electrons present in the outermost shell

Atomic size refers to the Radius of an atom or distance between the centre of nucleus and outmost shell of an isolated atom

Answer 2

valency is equal to the no of electrons present in valance shell for elements having valence electron 1;2;3 but for elements having valence electron more than 3 is equal to 8-no of valence electrons
atomic size is the distance between nucleus and outermost electron