Which is correct among the following statements?

Radius of \(Cl\) atom is \(0.99 Å\) while that of \(Na\) atom is \(1.54 Å\).

The correct answer is option 2. Radius of \(Cl\) atom is \(0.99 Å\) while that of \(Na\) atom is \(1.54 Å\).

To understand which statement is correct, let's dive into the typical values for atomic and ionic radii and their trends.

Atomic and Ionic Radii

Chlorine (Cl)

Atomic Radius: The radius of a chlorine atom is approximately 0.99 Å.

Ionic Radius: When chlorine gains an electron to form a chloride ion (\(Cl^-\)), the radius increases due to added electron-electron repulsion and the decreased effective nuclear charge per electron. The radius of \(Cl^-\) is around 1.81 Å.

Sodium (Na)

Atomic Radius: The radius of a sodium atom is approximately 1.54 Å.

Ionic Radius: When sodium loses an electron to form a sodium ion (\(Na^+\)), the radius decreases significantly because the loss of an electron reduces repulsion among the remaining electrons and the remaining electrons feel a stronger pull from the nucleus. The radius of \(Na^+\) is around 0.95 Å.

Evaluating the Statements

1. Radius of \(Cl\) atom is \(0.99 Å\) while that of \(Cl^+\) ion is \(1.54 Å\): This statement is incorrect. When a \(Cl\) atom loses an electron to become \(Cl^+\), its radius should decrease, not increase. The radius of \(Cl^+\) would be smaller than that of a neutral \(Cl\) atom, not larger.

2. Radius of \(Cl\) atom is \(0.99 Å\) while that of \(Na\) atom is \(1.54 Å\): This statement is correct. The radius of a chlorine atom is about 0.99 Å, and the radius of a sodium atom is about 1.54 Å.

3. Radius of \(Cl\) atom is \(0.95 Å\) while that of \(Cl^-\) ion is \(0.81 Å\): This statement is incorrect. The radius of a \(Cl\) atom is approximately 0.99 Å, and the radius of \(Cl^-\) is around 1.81 Å, not 0.81 Å. \(Cl^-\) is larger than the neutral \(Cl\) atom due to increased electron-electron repulsion.

4. Radius of \(Na\) atom is \(0.95 Å\) while that of \(Na^+\) ion is \(1.54 Å\): This statement is incorrect. The radius of a sodium atom is about 1.54 Å, and the radius of \(Na^+\) is about 0.95 Å. When \(Na\) loses an electron to form \(Na^+\), the radius decreases.

Based on the typical values and trends for atomic and ionic radii, the correct statement is (2) Radius of \(Cl\) atom is \(0.99 Å\) while that of \(Na\) atom is \(1.54 Å\).