Absolutely any chemical substance that exists in nature is formed by a large number of identical particles that are interconnected. All substances exist in three states of aggregation: gaseous, liquid, and solid. When thermal motion is difficult (at low temperatures), as well as in solids, the particles are strictly oriented in space, which is manifested in their precise structural organization.
The crystal lattice of a substance is a structure with a geometrically ordered arrangement of particles (atoms, molecules or ions) at specific points in space. In various lattices, the interstitial space is distinguished and the nodes themselves are the points at which the particles themselves are located.
There are four types of crystal lattice: metal, molecular, atomic, and ionic. The types of gratings are determined in accordance with the type of particles located in their nodes, as well as the nature of the bonds between them.
A crystalline lattice is called molecular if molecules are located in its nodes. They are interconnected by relatively weak intermolecular forces, called van der Waals forces, however, the atoms themselves inside the molecule are joined by a significantly stronger covalent bond (polar or nonpolar). The molecular crystal lattice is characteristic of 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 just such a structure. The number of inorganic substances that are characterized by a molecular structure is very small. These are, for example, solid hydrogen halides, natural sulfur, ice, solid simple substances and some others.
When heated, relatively weak intermolecular bonds break down rather easily, therefore substances with such lattices have very low melting points and low hardness, they are insoluble or slightly soluble in water, their solutions practically do not conduct electric current, and are characterized by significant volatility. Minimum boiling and melting points are for substances from non-polar molecules.
A metal lattice is a crystal lattice whose nodes are formed by atoms and positive ions (cations) of a metal with free valence electrons (detached from atoms during the formation of ions) randomly moving in the bulk of the crystal. However, these electrons are essentially semi-free, since they can freely move only within the framework that this crystal lattice limits.
Electrostatic electrons and positive metal ions are mutually attracted, which explains the stability of the metal crystal lattice. The set of free moving electrons is called electron gas - it provides good electrical and thermal conductivity of metals. When an electric voltage appears, the electrons rush to the positive particle, participating in the creation of an electric current and interacting with ions.
The metal crystal lattice is characteristic mainly for elemental metals, as well as for compounds of various metals with each other. The main properties that are inherent in metal crystals (mechanical strength, volatility, melting point) fluctuate quite strongly. However, such physical properties as ductility, ductility, high electrical and thermal conductivity, and characteristic metallic luster are peculiar only exclusively to crystals with a metal lattice.