Van der waals force definition

London dispersion forces result from the coulombic interactions between instantaneous dipoles. They are weak intermolecular forces caused by attractions between very small dipoles in molecules. A weak attractive force between atoms or nonpolar molecules caused by an instantaneous dipole moment of one atom or molecule that induces a similar temporary dipole moment in adjacent atoms or molecules. Like ionic or covalent bonds, these attraction forces do not result from a chemical bond as they are comparatively weak and hence can be easily disturbed. The ldf is named after the german physicist fritz london. Sometimes the term is used to encompass all intermolecular forces, although some scientists only include among them the london dispersion force, debye force, and keesom force. However, traditionally the definition would include the single atoms of the. Forces due to covalent bonds or electrostatic interactions between ions or ionic groups with one another or with neutral molecules are not included. The dispersion force which in fact is an induced dipole induced dipole interaction depends on the polarisability of the interacting molecules and is inversely proportional to the sixth power of separation. Nevertheless, the strength of inertial forces, such as gravity and draglift, decrease to a greater extent. First, the molecules of some materials, although electrically neutral, may be permanent electric dipoles. An intermolecular force is a relatively weak force that holds molecules together.

As the number of electrons increases so does the size of the oscillating and induced dipoles, the size of the attractive forces. Dispersion forces are present between all molecules and atoms and are typically greater for heavier, more polarizable molecules and molecules with larger surface areas. Because of fixed distortion in the distribution of electric charge in the very structure of some molecules, one side of a molecule is always somewhat positive and the opposite side somewhat negative. A weak force of attraction between electrically neutral molecules that collide with or pass very close to each other.