What is the correct name for the ionic compound Ca3P2?

• A. calcium phosphate
• B. calcium(II) phosphide
• C. tricalcium diphosphide
• D. calcium phosphide

Answer: (D)

Verified step by step guidance

1. Identify the cation and anion in the compound Ca3P2. Here, Ca is calcium, which forms a cation with a charge of +2 (Ca^{2+}), and P is phosphorus, which forms an anion called phosphide with a charge of -3 (P^{3-}).
2. Determine the charges of the ions to understand the ratio in the formula. Calcium has a +2 charge, and phosphide has a -3 charge. The formula Ca3P2 balances these charges so that the total positive and negative charges are equal.
3. Recall the naming conventions for ionic compounds: the cation (metal) is named first using the element name, and the anion (nonmetal) is named second with the suffix '-ide'. Since calcium is an alkaline earth metal with a fixed charge of +2, no Roman numeral is needed.
4. Combine the names of the ions without prefixes because ionic compounds do not use prefixes to indicate the number of ions. The correct name is 'calcium phosphide'.
5. Verify that the other options are incorrect: 'calcium phosphate' refers to a different polyatomic ion (PO4^{3-}), 'calcium(II) phosphide' incorrectly uses a Roman numeral for calcium, and 'tricalcium diphosphide' incorrectly applies molecular prefixes to an ionic compound.