Final answer:
The formula for copper(II) phosphide is Cu3P2, which is achieved by combining three copper(II) ions with two phosphide ions to balance the charges and create a neutral compound.
Step-by-step explanation:
The formula for copper(II) phosphide is Cu3P2. Copper has a 2+ charge when it is in the copper(II) state, also known as cupric. Phosphide ions carry a 3- charge. To balance the charges and create a neutral compound, it takes three copper(II) ions (Cu2+) to balance with two phosphide ions (P3-), resulting in the formula Cu3P2.