Answer :

To determine which of the substances exhibit ionic bonding, let's analyze each one in turn:

1. KCl (Potassium Chloride):
- Potassium (K) is a metal, while Chlorine (Cl) is a non-metal.
- Ionic bonding typically occurs between metals and non-metals.
- In KCl, the metal potassium donates an electron to the non-metal chlorine, resulting in the formation of K+ and Cl− ions.
- Therefore, we expect ionic bonding in KCl.

2. SO2 (Sulfur Dioxide):
- Sulfur (S) and Oxygen (O) are both non-metals.
- Covalent bonding occurs between non-metals as they share electrons rather than transfer them.
- Thus, SO2 does not exhibit ionic bonding but rather covalent bonding.

3. HCl (Hydrochloric Acid):
- Hydrogen (H) is a non-metal, and Chlorine (Cl) is also a non-metal.
- The bond between hydrogen and chlorine is a covalent bond where electrons are shared, although it is a polar covalent bond due to the significant difference in electronegativity.
- Therefore, HCl does not exhibit ionic bonding.

4. CH3Cl (Chloromethane):
- Carbon (C), Hydrogen (H), and Chlorine (Cl) are all non-metals.
- The bonding here involves sharing of electrons rather than transfer, making it covalent bonding.
- Thus, CH3Cl does not exhibit ionic bonding.

After reviewing each substance, we see that only KCl is expected to have ionic bonding. Thus, the correct answer is:

KCl

The other substances (SO2, HCl, and CH3Cl) exhibit covalent bonding instead of ionic bonding.