Question 5 • IA-Chemistry A Survey of Chemistry A
Calcium forms Ca²⁺ ions, and phosphide forms P³⁻ ions. A neutral compound needs the total positive and negative charges to balance: three Ca²⁺ ions give +6, while two P³⁻ ions give −6. Therefore, calcium phosphide is Ca₃P₂, choice C.
AI-written and checked against the verified answer.