Which of the following chlorides is covalent ?

Options

A. `NaCl`
B. `BeCl_2`
C. `CaCl_2`
D. `BaCl_2`

Explanation

To determine which of the given chlorides is covalent among NaCl, BeCl2, CaCl2, and BaCl2, we can follow these steps:

### Step 1: Understand the nature of the chlorides
- We need to analyze the chlorides based on the nature of the metal ions involved. The metals can either form ionic or covalent bonds with chlorine.

### Step 2: Identify the charge of the metal ions
- Sodium (Na) has a charge of +1.
- Beryllium (Be), Calcium (Ca), and Barium (Ba) have a charge of +2.

### Step 3: Consider the polarizing power of the metal ions
- Polarizing power is the ability of a cation to distort the electron cloud of an anion. It depends on two factors:
1. The charge of the cation: Higher charge means higher polarizing power.
2. The size of the cation: Smaller size means higher polarizing power.

### Step 4: Compare the polarizing power of the cations
- Among the cations:
- Na+ has a charge of +1 and is larger in size.
- Be2+ has a charge of +2 and is the smallest in size.
- Ca2+ and Ba2+ also have a charge of +2, but they are larger than Be2+.

### Step 5: Determine which chloride is covalent
- Since Be2+ is the smallest cation with the highest charge, it has the greatest polarizing power. This means that Be2+ can significantly distort the electron cloud of the chloride ion (Cl-), leading to a sharing of electrons.
- Therefore, BeCl2 will exhibit covalent character due to the high polarizing power of Be2+.

### Conclusion
- The chloride that is covalent among the options provided is **BeCl2** (Beryllium chloride).

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