Formula of Hydroxyapatite

Options

A. `(CaPO_4)_6.CaF_2`
B. `3[Ca(PO_4)_2].Ca(OH)_2`
C. `3[Ca_3(PO_4)_2].CaF_2`
D. `Ca_3(PO_4)_2].Ca(OH)_2`

Answer

To determine the formula of hydroxyapatite, we can break down the components involved in its structure. Hydroxyapatite is a naturally occurring mineral form of calcium apatite, which is a critical component of bone and teeth.

### Step-by-Step Solution:

1. **Identify the Components**: Hydroxyapatite is primarily composed of calcium (Ca), phosphate (PO4), and hydroxide (OH) ions.

2. **Calcium Ions**: The formula starts with calcium ions. Hydroxyapatite contains three calcium ions. Therefore, we write this as \( Ca^{2+} \).

3. **Phosphate Ions**: Next, we have phosphate ions. Hydroxyapatite contains two phosphate groups. The phosphate ion has the formula \( PO_4^{3-} \). Since there are two phosphate groups, we write this as \( (PO_4)_{2} \).

4. **Hydroxide Ions**: Finally, hydroxyapatite contains one hydroxide ion, which is represented as \( OH^{-} \).

5. **Combine the Components**: Now, we can combine all these components into a single formula. The overall formula for hydroxyapatite becomes:
\[ Ca_3(PO_4)_2(OH) \]

### Final Formula:
Thus, the formula of hydroxyapatite is \( Ca_3(PO_4)_2(OH) \).