Which one is a covalent compound?
(a)HCl
(b)NaCl
(c)KCl
(d)`MgCl_(2)`

Options

A. HCI
B. NaCl
C. KCI
D. `MgCl_2`

Explanation

To determine which of the given compounds is a covalent compound, we need to analyze each option based on the nature of the elements involved (metals vs. non-metals) and the type of bonding that occurs.

### Step-by-Step Solution:

1. **Understand the Definition of Covalent Compounds**:
- Covalent compounds are formed when two non-metals share electrons to achieve a full outer shell (octet).

2. **Analyze Each Option**:
- **(a) HCl**:
- Hydrogen (H) is a non-metal and Chlorine (Cl) is also a non-metal.
- Since both are non-metals, they will share electrons, forming a covalent bond.
- Therefore, HCl is a covalent compound.

- **(b) NaCl**:
- Sodium (Na) is a metal and Chlorine (Cl) is a non-metal.
- In this case, sodium donates an electron to chlorine, resulting in an ionic bond.
- Therefore, NaCl is not a covalent compound.

- **(c) KCl**:
- Potassium (K) is a metal and Chlorine (Cl) is a non-metal.
- Similar to NaCl, potassium donates an electron to chlorine, resulting in an ionic bond.
- Therefore, KCl is not a covalent compound.

- **(d) MgCl₂**:
- Magnesium (Mg) is a metal and Chlorine (Cl) is a non-metal.
- Magnesium donates electrons to chlorine, leading to the formation of ionic bonds.
- Therefore, MgCl₂ is not a covalent compound.

3. **Conclusion**:
- After analyzing all options, the only compound that is a covalent compound is **(a) HCl**.

### Final Answer:
The covalent compound among the given options is **(a) HCl**.

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