Noble gases are named because of their inertness towards reactivity. Identify an incorrect statement about them.

The correct option is "Noble gases have very high melting and boiling points."

Let us break down the scientific concepts to understand why this statement is incorrect, thereby making it the right choice for this question.

1. Understanding Noble Gases and Interatomic Forces
Noble gases (helium, neon, argon, krypton, xenon, and radon) belong to Group 18 of the periodic table. They have completely filled valence electron shells (a stable octet or duplet configuration). Because of this stable electronic configuration, noble gas atoms do not readily form covalent or ionic bonds with other atoms to form molecules. They exist as monoatomic gases under standard conditions.

Since they are monoatomic and non-polar, the only intermolecular (or interatomic) forces acting between them are weak London dispersion forces (a type of van der Waals force). These dispersion forces arise due to temporary, instantaneous fluctuations in electron density that create short-lived dipoles in neighboring atoms.

2. Analyzing Melting and Boiling Points
The magnitude of melting and boiling points of a substance depends directly on the strength of the forces holding its constituent particles together. Because the dispersion forces between noble gas atoms are extremely weak, very little thermal energy is required to overcome these forces and transition them from solid to liquid, or liquid to gas. As a result, noble gases have extremely low melting and boiling points, not very high ones. For example, helium has the lowest boiling point of any known substance at approximately:
$$4.2\mathrm{K}$$
Therefore, the statement "Noble gases have very high melting and boiling points" is false (incorrect).

3. Verifying the Other Options
To be absolutely thorough, let us look at why the other statements are correct:
• "Noble gases are sparingly soluble in water.": This is correct. Noble gases are non-polar, whereas water is a highly polar solvent. They can only dissolve in water through weak dipole-induced dipole interactions, making their solubility very low (sparingly soluble).
• "Noble gases have weak dispersion forces.": This is correct. As discussed, because they are monoatomic and neutral, they only experience weak temporary dipole-induced dipole interactions (dispersion forces).
• "Noble gases have large positive values of electron gain enthalpy.": This is correct. Because noble gases already possess stable, completely filled electronic shells, adding an electron requires overcoming strong interelectronic repulsion and putting the electron into a higher energy shell. This process requires an input of energy, leading to a large positive electron gain enthalpy value.