Identify the formula for the ionic compound calcium phosphate.
A. CA3(PO4)2
B. CaPO 4
The Correct Answer and Explanation is:
The correct formula for calcium phosphate is A. Ca₃(PO₄)₂.
Explanation:
Calcium phosphate is an ionic compound that consists of calcium ions (Ca²⁺) and phosphate ions (PO₄³⁻). To determine the correct formula, it’s important to balance the charges of the ions so that the compound is neutral overall.
- Calcium Ion (Ca²⁺):
- Calcium typically forms a Ca²⁺ ion, meaning it has a +2 charge.
- Phosphate Ion (PO₄³⁻):
- Phosphate is a polyatomic ion, and its formula is PO₄³⁻, meaning it has a -3 charge.
Balancing the Charges:
To form a neutral compound, the total positive charge must equal the total negative charge. Let’s balance the charges:
- The calcium ion has a +2 charge, and we need to balance it with phosphate ions, which have a -3 charge.
- If we place 3 calcium ions (Ca²⁺), their total positive charge will be +6 (since 3 × 2 = 6).
- To balance this +6 charge, we need 2 phosphate ions (PO₄³⁻), as each phosphate ion has a -3 charge, and 2 phosphate ions will give us a total negative charge of -6 (since 2 × -3 = -6).
Thus, the formula for calcium phosphate is Ca₃(PO₄)₂, where the 3 calcium ions balance the 2 phosphate ions, resulting in a neutral compound.
Why not CaPO₄?
The formula CaPO₄ would not correctly balance the charges. A single calcium ion (Ca²⁺) would only neutralize one phosphate ion (PO₄³⁻) in terms of charge, but this would leave the compound with an overall charge imbalance. Therefore, CaPO₄ is not the correct formula.
In conclusion, the correct formula for calcium phosphate is Ca₃(PO₄)₂, as it balances the charges between the calcium and phosphate ions.