Group 18 consists of elements: helium, neon, argon, krypton, xenon, radon and oganesson. All these are gases and chemically unreactive. They form very few compounds, because of this they are termed as noble gases. All noble gases have general electronic configuration ns²np⁶ except helium which has 1s². Many of the properties of noble gases including their inactive nature are ascribed to their closed shell structures. Due to stable electronic configuration these gases exhibit very high ionization enthalpy. However, it decreases down the group with increase in atomic size. Atomic radii increase down the group with increase in atomic number. Since noble gases have stable electronic configurations, they have no tendency to accept the electron and therefore, have large positive values of electron gain enthalpy.

Which of the following noble gases is most soluble in water?

Radon

The correct answer is option 2. Radon.

The solubility of a gas in water depends on factors such as the gas's molecular weight, polarity, and intermolecular forces. Among noble gases, radon (Rn) has the highest molecular weight, making it the most soluble in water compared to lighter noble gases like helium (He), neon (Ne), and krypton (Kr).

Here is an explanation of why radon is the most soluble noble gas in water:

Molecular Weight: Radon has the highest atomic number and atomic mass among the noble gases. Its heavier mass allows it to interact more strongly with water molecules, increasing its solubility.

Polarizability: Radon atoms are larger and have more electrons compared to lighter noble gases. This increased electron density and size make radon more polarizable, meaning it can induce temporary dipoles in nearby water molecules more effectively. As a result, radon molecules can interact more strongly with water molecules, leading to higher solubility.

Intermolecular Forces: The solubility of gases in water is also influenced by the strength of intermolecular forces. Radon's larger size and higher atomic mass enable it to participate in stronger London dispersion forces with water molecules, enhancing its solubility compared to lighter noble gases like helium and neon.

Overall, due to its higher molecular weight, greater polarizability, and stronger intermolecular forces, radon is the most soluble noble gas in water among the options provided.