The formula formed when calcium ion reacts with carbonate ion is

Options

A. `Ca_2CO_3`
B. `CaCO_3`
C. `Ca(CO_3)_2`
D. `Ca_3(CO_3)_2`

Explanation

To determine the formula formed when a calcium ion reacts with a carbonate ion, follow these steps:

### Step-by-Step Solution:

1. **Identify the Ions**:
- The calcium ion is represented as \( \text{Ca}^{2+} \).
- The carbonate ion is represented as \( \text{CO}_3^{2-} \).

2. **Understand the Charges**:
- The calcium ion has a charge of +2.
- The carbonate ion has a charge of -2.

3. **Combine the Ions**:
- Since the charges of the calcium ion and the carbonate ion are equal in magnitude but opposite in sign, they can combine to form a neutral compound.

4. **Write the Chemical Formula**:
- When combining the ions, we write the formula by placing the cation (calcium) first followed by the anion (carbonate).
- Therefore, the formula for the compound formed is \( \text{CaCO}_3 \).

5. **Conclusion**:
- The final answer is that the formula formed when calcium ion reacts with carbonate ion is \( \text{CaCO}_3 \), which is known as calcium carbonate.