molekyylienvälisiin

Intermolecular forces are the attractive or repulsive forces that exist between neighboring molecules. These forces are distinct from intramolecular forces, which are the forces that hold atoms together within a molecule, such as covalent or ionic bonds. Intermolecular forces are significantly weaker than intramolecular forces, but they play a crucial role in determining the physical properties of substances, including their boiling points, melting points, viscosity, and surface tension.

There are several types of intermolecular forces. London dispersion forces, also known as van der Waals forces, are the weakest and arise from temporary fluctuations in electron distribution within molecules, creating instantaneous dipoles. These forces are present in all molecules, but they become more significant as the size and number of electrons in a molecule increase. Dipole-dipole forces occur between polar molecules, which have permanent uneven distributions of electron density. The positive end of one polar molecule is attracted to the negative end of another. Hydrogen bonds are a special type of dipole-dipole interaction that occurs when a hydrogen atom is bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine. These bonds are stronger than other dipole-dipole forces and are responsible for many of water's unique properties. Ion-dipole forces occur between an ion and a polar molecule, such as when salt dissolves in water. The charged ion is attracted to the oppositely charged end of the polar molecule. The collective strength of these intermolecular forces dictates whether a substance exists as a solid, liquid, or gas at a given temperature and pressure.