why some substances sublime? why liquid state doesnot exist in iodine, napthalene etc. ???

Dear deeksha,

Sublimation is the transition of a substance from the solid phase to the gas phase without passing through an intermediate liquid phase. The reverse process is also known as Deposition. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point in its phase diagram.

It basically has to do with the mass and dispersion forces. Iodine has the most mass and the most electrons, so it has the strongest dispersion forces and so is able to exist as a solid.

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