Final answer:
The difference in boiling points between I₂ and SO₂ is primarily due to the stronger London dispersion forces in I₂ owing to its higher molar mass and larger molecular size.
Step-by-step explanation:
The most important intermolecular force in determining the difference in the boiling points of I₂ and SO₂ is the London dispersion force. Iodine (I₂) has a much higher molar mass (253.8 g/mol) compared to sulfur dioxide (SO₂, 64.1 g/mol), which means that Iodine will exhibit stronger dispersion forces due to increased molecular size and surface area. These stronger dispersion forces in I₂ result in a higher amount of energy required to overcome these forces, leading to a higher boiling point in comparison with SO₂. Moreover, while SO₂ is a polar molecule and exhibits dipole-dipole interactions, these are weaker than the dispersion forces in a much larger molecule like I₂.
Consequently, even though SO₂ has dipole-dipole interactions, the dispersion forces in I₂ are dominant in determining the boiling point between these two molecules.