Solids exist in a crystalline and amorphous state and predominantly have a crystalline structure. It is distinguished by the correct location of particles at precisely defined points, characterized by periodic repeatability in volumetric, three-dimensional space. If we mentally connect these points with straight lines, we get a spatial framework, which is called a crystal lattice. The concept of "crystal lattice" refers to a geometric image that describes three-dimensional periodicity in the placement of molecules (atoms, ions) in crystalline space.
Particle locations are called lattice nodes. Inside the framework there are inter-node communications. The type of particles and the nature of the bond between them: molecules, atoms, ions - determine the type of crystal lattice. In total, four such types are distinguished: ionic, atomic, molecular and metallic.
If ions are located in the lattice sites (particles with a negative or positive charge), then this is an ionic crystal lattice characterized by bonds of the same name.
These bonds are very strong and stable. Therefore, substances with this type of structure have a sufficiently high hardness and density, non-volatility and refractory. At low temperatures, they manifest themselves as dielectrics. However, upon melting of such compounds, the geometrically regular ionic crystal lattice (ion arrangement) is broken and the strength bonds decrease.
At a temperature close to the melting point, ion-bound crystals are already capable of conducting an electric current. Such compounds are readily soluble in water and other liquids that are composed of polar molecules.
The ionic crystal lattice is characteristic of all substances with an ionic type of bond - salts, metal hydroxides, binary compounds of metals with non-metals. The ionic bond has no directivity in space, because each ion is immediately bound to several counterions, the interaction force of which depends on the distance between them (Coulomb law). Ion-bonded compounds have a non-molecular structure, they are solids with ionic lattices, high polarity, high melting and boiling points, which are electrically conductive in aqueous solutions. In its pure form, compounds with ionic bonds practically do not occur.
The ionic crystal lattice is inherent in certain hydroxides and oxides of typical metals, salts, i.e. substances with ionic chemical bonds.
In addition to the ionic bond in crystals, there is a metal, molecular and covalent bond.
Crystals having a covalent bond are semiconductors or dielectrics. Typical examples of atomic crystals are diamond, silicon and germanium.
Diamond is a mineral, allotropic cubic modification (form) of carbon. The crystal lattice of diamond is atomic, very complex. At the nodes of such a lattice are atoms interconnected by extremely strong covalent bonds. A diamond consists of individual carbon atoms located one at a time in the center of a tetrahedron, the vertices of which are the four nearest atoms. Such a lattice is characterized by a face-centered cubic unit cell, which determines the maximum hardness of diamond and a rather high melting point. There are no molecules in the diamond lattice - and the crystal can be considered as one impressive molecule.
In addition, the atomic crystal lattice is characteristic of silicon, solid boron, germanium, and compounds of individual elements with silicon and carbon (silica, quartz, mica, river sand, carborundum). In general, there are relatively few representatives of crystalline bodies with an atomic lattice.