Question

Noble gases are sparingly soluble in water, owing to (a) hydrogen bonding (b) dipole-dipole interactions (c) dipole-induced dipole interactions (d) induced dipole-instantaneous dipole interactions

Short answer

(d) induced dipole-instantaneous dipole interactions.

Step-by-step solution

Define Noble Gases and Water Interaction

Noble gases are chemically inert because of their complete valence electron shell, meaning they do not easily form bonds. When dispersed in water, noble gases primarily interact with water molecules through non-polar and weak forces, due to the lack of hydrogen bonding or permanent dipoles.

Eliminate Irrelevant Interactions

Since hydrogen bonding requires a hydrogen atom bonded to a highly electronegative atom, option (a) can be ruled out. Dipole-dipole interactions (option b) require polar molecules, which noble gases are not.

Consider Dipole-Induced Dipole Interactions

Dipole-induced dipole interactions occur when a polar molecule induces a temporary dipole in a non-polar molecule. Although water is polar, noble gases remain non-polar, making these interactions possible but not primary.

Identify Induced Dipole-Instantaneous Dipole Interactions

Induced dipole-instantaneous dipole interactions, also known as London dispersion forces, occur between all molecules, including non-polar ones like noble gases. These forces are the predominant interaction in noble gases dissolved in water, due to the commonality of instantaneous dipoles in the absence of strong permanent dipoles.

Conclusion

The most accurate description of the interaction between noble gases and water involves the temporary fluctuations of electron density that lead to induced dipole-instantaneous dipole interactions, aligning with option (d).

Key concepts

Induced Dipole-Instantaneous Dipole Interactions

Induced dipole-instantaneous dipole interactions are a fascinating aspect of chemistry, especially when considering noble gases. These interactions occur when a temporary or instantaneous dipole in one atom induces a dipole in a neighboring atom. This happens due to the constant motion of electrons around the nucleus. Electrons are never stationary; they move rapidly and can momentarily form dips in electron density, creating a temporary dipole.

When a temporary dipole forms, it can influence nearby atoms or molecules. Even noble gases, which are usually inert, can participate in these types of interactions. These forces arise because every electron in a molecule can contribute to an instantaneous dipole at any moment. This results in a weak attraction that plays a significant role in the solubility of noble gases in water. Such interactions are subtle and fleeting, occurring in the absence of other stronger forces.

So, while noble gases do not engage in more permanent chemical bonds, they can still have these temporary attractions, highlighting the dynamic nature of electron behavior. This interaction type helps explain how noble gases can be dissolved in water, despite their inertness.

London Dispersion Forces

London dispersion forces, also known as Van der Waals forces, are a type of temporary attractive force. These forces are prevalent among all molecules; however, they play a crucial role in non-polar substances like noble gases. When atoms or molecules attract due to fluctuations in electron distribution, they are experiencing London dispersion forces.

These forces occur universally because every molecule, regardless of polarity, can experience changes in electron distribution. In noble gases, these forces are perhaps the only type of interaction present since noble gases lack permanent dipoles. This type of force is typically weak but can be significant when large numbers of atoms are involved or when they are confined to small spaces, like being dissolved in water.

The magnitude of London dispersion forces increases with the number of electrons in a molecule. Thus, larger noble gases have stronger London dispersion forces. This explains why heavier noble gases are more easily soluble in water compared to lighter ones. London dispersion forces remind us that even the simplest of atoms can have complex behaviors due to transient electron motion.

Chemical Interactions of Noble Gases

Despite being renowned for their lack of reactivity, noble gases do engage in certain chemical interactions, although these are limited compared to other elements. Noble gases possess a full valence shell of electrons, making them chemically inert and stable; however, they can still undergo physical phenomena like those induced by temporary forces.

The key interactions for noble gases involve weak forces such as London dispersion forces. These weak forces result in attractions that can lead noble gases to exhibition behaviors like solubility in water. When dissolved in water, noble gases do not form new chemical bonds but interact through induced dipole moment mechanisms as discussed previously.

This instills an understanding that while noble gases physically interact within solids and liquids, they do not partake in chemical reactions as would other, less stable elements. The chemical interactions of noble gases are a prime example of how even inert substances can have nuanced behaviors, thanks to the principles of atomic and molecular physics.