* Strong van der Waals forces: Naphthalene is a nonpolar molecule with a large surface area. This allows for strong London dispersion forces, a type of van der Waals force, to develop between molecules. These forces require significant energy to overcome, contributing to the high boiling point.

* Planar structure and stacking: The planar structure of naphthalene allows for efficient stacking of molecules, maximizing the surface area interactions and further strengthening the van der Waals forces.

* Molecular weight: Naphthalene has a relatively high molecular weight (128 g/mol). Larger molecules generally have stronger intermolecular forces, which contributes to a higher boiling point.

In summary: The combination of strong van der Waals forces, efficient stacking due to its planar structure, and a relatively high molecular weight all contribute to naphthalene's high boiling point.