Which of the following is the correct chemical formula for calcium phosphide?

• A. Ca2P
• B. Ca2P3
• C. Ca3P2
• D. CaP2

Answer: (C)

Verified step by step guidance

1. Identify the ions involved: calcium typically forms a Ca^{2+} ion, and phosphide is the P^{3-} ion.
2. Determine the ratio of calcium ions to phosphide ions needed to balance the charges so the compound is electrically neutral.
3. Set up the charge balance equation: (number of Ca^{2+} ions) \times (+2) + (number of P^{3-} ions) \times (-3) = 0.
4. Find the smallest whole number ratio of Ca^{2+} to P^{3-} ions that satisfies the charge balance. This ratio is 3 calcium ions to 2 phosphide ions.
5. Write the chemical formula using the ratio found: Ca_{3}P_{2}.