There are three atoms in lithium oxide: two lithium atoms and one oxygen atom. This can be determined by looking at the chemical formula for lithium oxide, which is Li2O. The subscript 2 after the lithium (Li) indicates that there are two lithium atoms in one molecule of lithium oxide. The lack of a subscript after the oxygen (O) indicates that there is only one oxygen atom in one molecule of lithium oxide. Therefore, there are two lithium atoms and one oxygen atom in a molecule of lithium oxide, for a total of three atoms.