Analyze Statement I

Statement I says: In $\mathrm{Cl}_2$ molecule the covalent radius is double of the atomic radius of chlorine.

• For a homonuclear diatomic molecule like $\mathrm{Cl}_2$, $\text{bond length} = 2 \times \text{covalent radius}.$
• Hence, $\text{covalent radius} = \frac{1}{2}(\text{Cl-Cl bond length}).$

The statement claims: $\text{covalent radius} = 2 \times \text{atomic radius}.$

This is not correct. In fact, atomic radius and covalent radius are different quantities, and for chlorine the covalent radius is not double the atomic radius. Rather, in a diatomic molecule, bond length is double the covalent radius.

Therefore, Statement I is incorrect.

Analyze Statement II

Statement II says: Radius of anionic species is always greater than their parent atomic radius.

• When an atom gains one or more electrons to form an anion, the number of electrons increases while nuclear charge remains the same.
• This increases electron-electron repulsion and decreases the effective pull per electron.
• Hence, the electron cloud expands.

Therefore, $r(\text{anion}) > r(\text{parent atom}).$

So, Statement II is correct.

Choose the correct option

• Statement I: Incorrect
• Statement II: Correct

Hence, the correct option is: $\boxed{\text{D}}$

Comparison with stored answer

Stored correct answer: $\text{D}$

My derived answer: $\text{D}$

They match.