The crystal lattice and its main types

Absolutely, any chemical substance that exists in nature is formed by a large number of identical particles that are related to each other. All substances exist in three aggregate states: gaseous, liquid and solid. When thermal motion is difficult (at low temperatures), and also in solids, the particles are strictly oriented in space, which is manifested in their precise structural organization.

A crystal lattice of matter is a structure with a geometrically ordered arrangement of particles (atoms, molecules or ions) at certain points of space. In different lattices distinguish between interstitial space and directly nodes - the points at which the particles themselves are located.

The crystal lattice is of four types: metallic, molecular, atomic, ionic. The types of lattices are determined in accordance with the type of particles located in their nodes, as well as the nature of the connections between them.

A crystal lattice is called molecular lattice in the case when molecules are located at its nodes. They are interconnected by intermolecular relatively weak forces, called van der Waals forces, but the atoms inside the molecule themselves are connected by a much stronger covalent bond (polar or nonpolar). Molecular crystal lattice is inherent in chlorine, solid hydrogen, carbon dioxide and other substances that are gaseous at ordinary temperature.

Crystals that form noble gases also have molecular lattices consisting of monatomic molecules. Most solid organic substances have exactly this structure. The number of inorganic substances, which is inherent in the molecular structure, is very small. This, for example, solid halogenated hydrogen, natural sulfur, ice, solid simple substances and some others.

When heated relatively weak intermolecular bonds are destroyed quite easily, therefore, substances with such lattices have very low melting points and low hardness, they are insoluble or slightly soluble in water, solutions they practically do not conduct electric current, are characterized by considerable volatility. Minimum boiling and melting points are for substances from nonpolar molecules.

Metallic is a crystal lattice whose nodes are formed by atoms and positive ions (cations) of a metal with free valence electrons (disengaged from atoms when ions are formed) randomly moving in the bulk of the crystal. However, these electrons are essentially semi-free, since they can move freely only within the limits that this crystal lattice limits.

Electrostatic electrons and positive metal ions are mutually attracted, which explains the stability of the metallic crystal lattice. A set of free moving electrons is called an electron gas - it provides good electrical and thermal conductivity of metals. With the appearance of an electrical voltage, the electrons rush to the positive particle, participating in the creation of an electric current and interacting with ions.

The metallic crystal lattice is characteristic mainly for elementary metals, as well as for compounds of different metals with each other. The main properties that are inherent in metallic crystals (mechanical strength, volatility, melting point) fluctuate sufficiently. However, such physical properties as plasticity, ductility, high electrical and thermal conductivity, characteristic metallic luster are peculiar only to crystals with a metal lattice.