how do i find the formula for lithium oxide

Answer 1

Lithium is in Group IA and therefore has a charge (oxidation number)

of +1.

Oxygen is in Group VIA and therefore has a -2 or 2- depening on how you prefer to say it. The idea for a compound is that the opposing charges cancel each other . That means you need 2 of the +1 to equal the -2 so it is Li₂O