van der Waals radius of chlorine is less than that of covalent radius.

Explanation

To determine whether the statement "the van der Waals radius of chlorine is less than that of covalent radius" is correct or incorrect, we can analyze the definitions and characteristics of both types of radii.

### Step-by-Step Solution:

1. **Understanding Covalent Radius**:
- The covalent radius is defined as the distance between the nuclei of two bonded atoms divided by two. For chlorine (Cl), this radius is measured when two chlorine atoms are covalently bonded together.
- Mathematically, if the distance between the two chlorine nuclei in a Cl2 molecule is 'd', then the covalent radius (R_covalent) is given by:
\[ R_{covalent} = \frac{d}{2} \]

2. **Understanding Van der Waals Radius**:
- The van der Waals radius refers to the size of an atom when it is not bonded to another atom. It represents the distance at which the electron clouds of two non-bonded atoms begin to overlap.
- For chlorine, if we consider two non-bonded chlorine atoms, the distance between their nuclei is greater than in the bonded state. Thus, the van der Waals radius (R_van der Waals) is also calculated as half the distance between the two nuclei:
\[ R_{van der Waals} = \frac{D}{2} \]
- Here, 'D' is the distance between the two non-bonded chlorine nuclei.

3. **Comparing the Two Radii**:
- In general, the van der Waals radius is larger than the covalent radius because in a bonded state (covalent), the atoms are closer together due to the attraction between them, while in a non-bonded state (van der Waals), they are further apart.
- Therefore, we can conclude:
\[ R_{van der Waals} > R_{covalent} \]

4. **Evaluating the Statement**:
- The statement claims that the van der Waals radius of chlorine is less than the covalent radius. Based on our analysis, this is incorrect.
- Thus, we conclude that the statement is **wrong**.

### Final Conclusion:
The van der Waals radius of chlorine is greater than the covalent radius, making the statement "the van der Waals radius of chlorine is less than that of covalent radius" incorrect.

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