Ioonkristallide

Ioonkristallide, also known as ionic crystals, are solid materials composed of ions held together by electrostatic forces. These forces, known as ionic bonds, arise from the attraction between oppositely charged ions. Typically, ionic crystals form when a metal atom, which readily loses electrons to become a positively charged cation, reacts with a nonmetal atom, which readily gains electrons to become a negatively charged anion. Examples include sodium chloride (NaCl) and magnesium oxide (MgO).

The structure of ionic crystals is characterized by a regular, repeating arrangement of cations and anions in a three-dimensional lattice. This arrangement maximizes the attractive forces between opposite charges and minimizes the repulsive forces between like charges. The specific crystal structure adopted depends on the relative sizes and charges of the constituent ions. Common structures include the rock salt structure, cesium chloride structure, and zinc blende structure.

Ionic crystals generally exhibit distinct physical properties. They are typically hard and brittle, meaning they resist scratching but fracture easily when subjected to stress. This brittleness arises from the displacement of ions within the lattice; if a layer of ions is shifted, like charges can align, leading to strong repulsive forces and fracture. In their solid state, ionic crystals are electrical insulators because the ions are fixed in their lattice positions and cannot move freely to conduct electricity. However, when molten or dissolved in a suitable solvent, the ions become mobile and can carry electric charge, making the liquid or solution electrically conductive. Ionic compounds usually have high melting and boiling points due to the strong electrostatic forces holding the ions together.