Answer
$Cu_2O$
Work Step by Step
Look at the charges of each ion in copper (I) oxide in order to determine the chemical formula. While metals can have a variety of different charges, the "(I)" tells us that Copper has a charge of 1+. On the periodic table, oxygen is located two groups to the left of the noble gases, meaning that it has a charge of -2. Since the magnitude of the oxygen's charge is twice as great as that of Copper(I), there must be two copper atoms for every one oxygen atom. Thus, the chemical formula for Copper (I) Oxide is $Cu_2O$.
