Which amongst the following contains a covalent bond?

Options

A. `MgCl_(2)`
B. `CaF_(2)`
C. `Al_(2)O_(3)`
D. `HCl`

Answer

To determine which of the given compounds contains a covalent bond, we can follow these steps:

### Step 1: Understand the Concept of Electronegativity
Electronegativity is a measure of an atom's ability to attract and hold onto electrons. The difference in electronegativity between two atoms can help us determine the type of bond that forms between them.

### Step 2: Identify the Electronegativity Values
We need to know the electronegativity values of the elements in the compounds provided. Common values to remember are:
- Magnesium (Mg): 1.2
- Chlorine (Cl): 3.0
- Calcium (Ca): 1.0
- Fluorine (F): 4.0
- Aluminum (Al): 1.5
- Oxygen (O): 3.5
- Hydrogen (H): 2.1

### Step 3: Calculate the Electronegativity Differences
Using the electronegativity values, we can calculate the differences for each compound:

1. **MgCl₂**:
- ΔEN = |3.0 (Cl) - 1.2 (Mg)| = 1.8 (greater than 1.7, ionic bond)

2. **CaF₂**:
- ΔEN = |4.0 (F) - 1.0 (Ca)| = 3.0 (greater than 1.7, ionic bond)

3. **Al₂O₃**:
- ΔEN = |3.5 (O) - 1.5 (Al)| = 2.0 (greater than 1.7, ionic bond)

4. **HCl**:
- ΔEN = |3.0 (Cl) - 2.1 (H)| = 0.9 (less than 1.7, covalent bond)

### Step 4: Determine the Type of Bond
From the calculations:
- MgCl₂, CaF₂, and Al₂O₃ have differences greater than 1.7, indicating they are ionic compounds.
- HCl has a difference of 0.9, indicating it has a covalent bond.

### Conclusion
The compound that contains a covalent bond is **HCl**.

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