Final answer:
The correct formula for a compound with 2 atoms of lithium for every atom of oxygen is Li₂O, due to the +1 charge of lithium ions and the -2 charge of oxide ions, balanced in a 2:1 ratio.
Step-by-step explanation:
The proper formula for a compound that consists of 2 atoms of lithium for every atom of oxygen is Li₂O. This is because the lithium ion has a charge of +1 (Li⁺), and the oxide ion has a charge of -2 (O²⁻). To balance the charges, two lithium ions are needed for every oxide ion, which gives the formula for lithium oxide as Li₂O. An alternative method to determine this formula is the crisscross method, where you cross over the charges to become subscripts, ignoring the signs.