Molecular and Ionic Solids

Molecular solids are a type of crystalline solids which have molecules or atoms as their constituent particles and are held together by non-ionic intermolecular forces like hydrogen bonds, dispersion forces, or dipole–dipole interactions.

The strength of these intermolecular forces dictates the properties of molecular solids. Overall, these solids tend to be soft, have low melting points, and have low thermal and electrical conductivity.

Nonpolar or net nonpolar molecular solids like solid nitrogen or dry ice are primarily held together by weak dispersion forces. Such solids have very low melting points and sublime easily.

Polar molecular solids like ice and solid sulfur dioxide exhibit hydrogen bonds and dipole–dipole interactions. Such solids have comparatively higher melting points and exist as soft solids or volatile liquids at standard temperature and pressure.

Another example of how the strength of the intermolecular forces influences properties of molecular solids is illustrated by solid iodine.

The increased strength of certain intermolecular forces between larger molecules is reflected in iodine’s properties. Although they are both nonpolar solids, iodine’s melting point i