The compounds containing ionic bonds are known as ionic compounds. They are formed by the transfer of electrons from one atom to another. The ionic compounds are made up of positively charged ions (cations) and negatively charged ions (anions).
Which one of the following is an ionic compound?

Options

A. `"CCl"_4`
B. `H_3O^(+)`
C. KCl
D. `CO_2`

Explanation

To determine which of the given compounds is an ionic compound, we will analyze each option based on the characteristics of ionic bonding.

### Step-by-Step Solution:

1. **Understanding Ionic Compounds**:
- Ionic compounds are formed by the transfer of electrons from one atom to another, resulting in the formation of positively charged ions (cations) and negatively charged ions (anions).

2. **Analyzing the Options**:
- We need to evaluate each compound to see if it is formed by ionic bonds.

3. **Option 1: CCl₄ (Carbon Tetrachloride)**:
- Carbon (C) shares its electrons with chlorine (Cl) atoms to form covalent bonds.
- Since the bonds are formed by sharing electrons, CCl₄ is a covalent compound, not an ionic compound.

4. **Option 2: H₃O⁺ (Hydronium Ion)**:
- In H₃O⁺, oxygen shares electrons with hydrogen atoms, and the positive charge arises from the coordinate bond where oxygen donates a pair of electrons.
- The bonds here are also covalent, so H₃O⁺ is not an ionic compound.

5. **Option 3: KCl (Potassium Chloride)**:
- Potassium (K) has one electron in its outer shell (configuration: 2, 8, 1) and chlorine (Cl) has seven electrons in its outer shell (configuration: 2, 8, 7).
- Potassium loses one electron to achieve a stable electron configuration (like noble gas), becoming K⁺.
- Chlorine gains that electron to complete its octet, becoming Cl⁻.
- This transfer of electrons results in the formation of K⁺ and Cl⁻ ions, making KCl an ionic compound.

6. **Option 4: CO₂ (Carbon Dioxide)**:
- In CO₂, carbon shares electrons with oxygen to form double bonds.
- The bonds are covalent, so CO₂ is not an ionic compound.

7. **Conclusion**:
- Among the given options, KCl is the only compound that is formed through ionic bonding.

### Final Answer:
The ionic compound among the options is **KCl**.