HCl gas is covalent and NaCl is an ionic compound. This is because

Options

A. sodium is highly electropositive
B. hydrogen is a non-metal
C. HCl is a gas
D. electronegativity difference between H and Cl is less then 2.1

Explanation

To determine why HCl gas is covalent and NaCl is an ionic compound, we need to analyze the nature of the bonds formed in each compound based on electronegativity differences and electron sharing.

### Step-by-Step Solution:

1. **Understanding Ionic and Covalent Bonds**:
- Ionic bonds are formed when there is a significant difference in electronegativity between two atoms, leading to the transfer of electrons from one atom to another.
- Covalent bonds are formed when two atoms share electrons, usually when the electronegativity difference is small.

2. **Electronegativity of Elements**:
- Electronegativity is a measure of an atom's ability to attract and hold onto electrons.
- For hydrogen (H), the electronegativity is approximately 2.1.
- For chlorine (Cl), the electronegativity is approximately 3.0.
- For sodium (Na), the electronegativity is approximately 0.9.

3. **Calculating Electronegativity Differences**:
- For HCl:
- Difference = |Electronegativity of Cl - Electronegativity of H| = |3.0 - 2.1| = 0.9
- For NaCl:
- Difference = |Electronegativity of Cl - Electronegativity of Na| = |3.0 - 0.9| = 2.1

4. **Determining Bond Type**:
- In HCl, the electronegativity difference (0.9) is less than 2.1, indicating that the bond is covalent. This means that H and Cl share electrons to form the bond.
- In NaCl, the electronegativity difference (2.1) is equal to or greater than 2.1, indicating that the bond is ionic. This means that Na transfers an electron to Cl, resulting in the formation of Na+ and Cl- ions.

5. **Conclusion**:
- HCl is a covalent compound because it involves sharing of electrons due to a small electronegativity difference.
- NaCl is an ionic compound because it involves the transfer of electrons due to a large electronegativity difference.

### Final Answer:
HCl gas is covalent because the electronegativity difference between H and Cl is less than 2.1, leading to electron sharing. NaCl is ionic because the electronegativity difference between Na and Cl is greater than 2.1, leading to electron transfer.