The molecule is a particle which consists of two or more atoms connected by covalent communication. The molecule is electrically a neutral particle and bears the coupled electrons.
The molecule is the smallest particle of chemical which has all its properties. It has constant amount of the atoms united by chemical bonds i.e. has constant structure. The chemical identity of a molecule is expressed by a configuration and set of chemical bonds between its atoms. Between atoms of a molecule there are valent and non-valence interactions. The first provide the main properties and stability of a molecule, the second – significantly affect properties of molecules and as a result of substance which they form. In molecules recognize existence of dvukhchentrovy and multicenter communications (most often three-center and four-center).
The molecule represents a dynamic system in which atoms are material points and can make mechanical oscillating and rotary motions of rather equilibrium nuclear configuration. This configuration corresponds to a minimum of energy of a molecule and is considered as the system of harmonious oscillators.
Molecules consist of atoms. Their arrangement can be transferred by means of a structural formula. For transfer of structure of a molecule gross-formula is used. Some molecules, for example, of proteins, may contain hundreds of thousands of atoms. Molecules are studied in quantum chemistry, the theory of the structure of molecules. These branches of science actively use achievements of quantum physics. Now in chemistry such industry as molecular design develops. Now for definition of the structure of molecules of a certain substance diffraction methods are used. The X-ray diffraction analysis and diffraction of neutrons concern them. These methods are straight lines. There are also other methods: oscillatory spectroscopy, electronic paramagnetic and nuclear magnetic resonances.