Which of the following pairs of elements would most likely form a salt?

o and n

ca and mg

cl and li

h and he

A salt is an ionic compound which needs a positive charge ion and a negative ion charge to form a salt.This means that the pair of element should be a metal and non-metal.This is simply because metal atoms tend to lose negative charge electrons and form positive ions while non-metals tend to receive the electrons from the metal atom to form negative charge ions.So answer is Cl and Li.