molekyylikiteet

Molekyylikiteet (molecular crystals) are a type of crystalline solid where the constituent particles are discrete molecules held together by intermolecular forces. These forces are generally much weaker than the ionic or covalent bonds found in other crystal types. Common intermolecular forces include van der Waals forces (London dispersion forces, dipole-dipole interactions) and hydrogen bonds.

The physical properties of molecular crystals are a direct consequence of these weak intermolecular attractions. They typically have low melting and boiling points, are often soft, and can be poor conductors of electricity and heat. This is because relatively little energy is required to overcome the intermolecular forces and disrupt the crystal lattice. Many molecular solids are also volatile and can sublime easily.

Examples of molecular crystals include ice (water, H2O), where molecules are held together by hydrogen bonds, and dry ice (solid carbon dioxide, CO2), where molecules are bound by London dispersion forces. Other common substances like sugar (sucrose), iodine (I2), and naphthalene (mothballs) also form molecular crystals. The arrangement of molecules within the crystal lattice can vary, leading to different polymorphic forms with potentially different properties. The study of molecular crystals is important in fields such as materials science and solid-state chemistry, as their properties can be tailored by modifying the molecular structure and the intermolecular interactions.