Final answer:
The expected compound formed from the reaction of lithium with oxygen is lithium oxide (Li₂O), and the sum of the subscripts in its formula, x + y, is 3.
Step-by-step explanation:
In the reaction of lithium with oxygen, lithium oxide (Li₂O) is the expected compound to be formed. According to the chemical formula, we can determine that the number of lithium ions (Li⁺) needed to balance the charge of one oxide ion (O²⁻) is two. By using the crisscross method, we can cross the charges of the ions, which leads to the empirical formula Li₂O for lithium oxide. In the provided compound notation LixOy, x would be 2, and y would be 1 because there are two lithium ions for every one oxygen ion. Therefore, the sum of x + y in this case would be 2 + 1 = 3.