∙ Valency is the combining capacity of an element and is determined by the number of valence electrons.
∙ When the number of valence electrons are four or less, valency is equal to the number of valence electrons.
∙ When the valence electrons are more than four, valency is obtained by subtracting the valence elctrons from eight.
AtomElectronic ConfigurationNo. of valency electronsValencyOxygen2,668 - 6 = 2Neon2,888 - 8 = 0Hydrogen111Aluminium2,8,333