Write the formula of lead phosphate.

To write the formula of lead phosphate, follow these steps:

1. **Identify the Ions Involved**:
- **Lead ion**: Lead can form two common ions, \( \text{Pb}^{2+} \) and \( \text{Pb}^{4+} \). In this case, we’ll use the \( \text{Pb}^{2+} \) ion for lead phosphate.
- **Phosphate ion**: The phosphate ion is \( \text{PO}_4^{3-} \).

2. **Determine the Combining Ratio**:
To balance the charges of the ions, we need to find the correct ratio of lead ions to phosphate ions so that the overall charge is neutral.

- The lead ion has a charge of \( +2 \).
- The phosphate ion has a charge of \( -3 \).

To balance these charges, you need a combination where the total positive charge equals the total negative charge. The least common multiple of 2 and 3 is 6, so:

- You need 3 lead ions (each contributing \( +2 \times 3 = +6 \) charge).
- You need 2 phosphate ions (each contributing \( -3 \times 2 = -6 \) charge).

3. **Write the Formula**:
- For 3 lead ions: \( \text{Pb}^{2+} \) × 3
- For 2 phosphate ions: \( \text{PO}_4^{3-} \) × 2

Combining these, the formula for lead phosphate is \( \text{Pb}_3(\text{PO}_4)_2 \).