To determine valency of an element you look at the number of valence electrons
with elements that have valence electrons from 1-4 they can form the same number of bods
ex: 1 valence electron = 1 bond
3 valence electron = 3 bond
With elements that have valence electrons from 5 and up they can form a number of bonds to add up to 8 electrons (octet)
ex: 5 valence electron = 3 bond (8 - # valence electron)
7 valence electron = 1 bond
