What is the formula for copper(II) phosphide?
Give your answer in the form A#B# where the number is the subscript.
The Correct Answer and Explanation is:
The formula for copper(II) phosphide is Cu3P2.
To determine the formula of copper(II) phosphide, we start by examining the charges of copper and phosphorus ions in this compound.
- Copper Ion (Cu²⁺): The “(II)” in copper(II) phosphide indicates that copper has a +2 oxidation state, meaning each copper ion has a charge of +2. This ion is represented as ( \text{Cu}^{2+} ).
- Phosphide Ion (P³⁻): Phosphorus, when it forms an ion in compounds like phosphides, typically takes on a -3 charge. This ion is represented as ( \text{P}^{3-} ).
In an ionic compound, the total positive and negative charges must balance to make the compound neutral. Therefore, we need to combine copper ions and phosphide ions in a ratio that neutralizes the charges.
To find this ratio, we look for the least common multiple (LCM) of the charges on Cu²⁺ and P³⁻:
- The LCM of 2 and 3 is 6.
To achieve a neutral compound, we need a total of +6 charge from copper ions and -6 charge from phosphide ions:
- Copper ions: To achieve +6, we need three Cu²⁺ ions, as ( 3 \times (+2) = +6 ).
- Phosphide ions: To achieve -6, we need two P³⁻ ions, as ( 2 \times (-3) = -6 ).
Thus, the formula that balances the charges is Cu₃P₂, where three copper ions combine with two phosphide ions.
Summary:
- Copper(II) phosphide has a formula of Cu₃P₂, meaning three copper (Cu) atoms for every two phosphorus (P) atoms.
- The charges of the ions, ( \text{Cu}^{2+} ) and ( \text{P}^{3-} ), dictate this 3:2 ratio to achieve charge neutrality.
This approach of balancing ionic charges is fundamental to determining formulas for ionic compounds, ensuring that the resulting compound is electrically neutral.