Final answer:
The formula for lithium oxide, which requires balancing the +1 charge of lithium (Li+) with the -2 charge of oxide (O2-), is Li2O. This can be determined using the crisscross method, which confirms the same result after simplification.
Step-by-step explanation:
The formula for lithium oxide is determined by the charges of the lithium and oxide ions. Lithium has a +1 charge (Li+) and oxide has a -2 charge (O2-). To balance the charges, two lithium ions are needed for every one oxide ion, resulting in the formula Li2O.
The crisscross method can be used as an alternative way to write the formula for this ionic compound. In this method, the numerical value of the charge on the lithium ion would be crossed over to become the subscript of the oxide ion, and vice-versa. However, since the oxide ion has a charge of -2, and lithium has a charge of +1, the final formula using the crisscross method would also result in Li2O after simplifying the ratio to the lowest whole numbers. It is essential that ionic compound formulas result in neutral overall charge, hence the subscripts in the formula must reflect the balance of charges.