Ionic crystal lattice

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 three-dimensional space. If we mentally connect these points by straight lines - we obtain a spatial framework, which is called a crystal lattice. The term "crystal lattice" refers to a geometric image that describes the three-dimensional periodicity in the arrangement of molecules (atoms, ions) in crystalline space.

The locations of the particles are called lattice sites. Inside the framework, inter-node connections operate. The type of particles and the nature of the connection between them: molecules, atoms, ions - determine the type of crystal lattice. In total, four types are distinguished: ionic, atomic, molecular and metallic.

If there are ions in the lattice sites (particles with a negative or positive charge), then this is an ionic crystal lattice characterized by the same bonds.

These connections are very strong and stable. Therefore, substances with this type of structure have a sufficiently high hardness and density, non-volatile and refractory. At low temperatures they manifest themselves as dielectrics. However, when melting such compounds, the geometrically correct ionic crystal lattice (ion arrangement) is violated and the strength bonds are reduced.

At a temperature close to the melting point, crystals with an ionic bond are already capable of conducting electric current. Such compounds are readily soluble in water and other liquids, which consist 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 nonmetals. The ionic bond does not have an orientation in space, because each ion is associated with several counterions at once, the interaction force of which depends on the distance between them (Coulomb's law). Ion-bound compounds have a non-molecular structure, they are solids with ionic lattices, high polarity, high melting and boiling points, in aqueous solutions being electrically conductive. Compounds with ionic bonds in pure form practically do not occur.

Ionic crystal lattice is inherent in some 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 metallic, molecular, and covalent bond.

Crystals that have 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 a diamond is atomic, very complex. At the nodes of such a lattice are atoms, interconnected by extremely strong covalent bonds. The diamond consists of individual carbon atoms, located one at the center of the tetrahedron, the tops 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 the 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 inherent in silicon, solid boron, germanium and compounds of individual elements with silicon and carbon (silica, quartz, mica, river sand, carborundum). In general, representatives of crystalline bodies with an atomic lattice are relatively few.