In most ionic compounds, the anions are much larger than the cations, and it is the anions which form the crystal array. The smaller cations reside in the holes between the anions.
1. Ions are assumed to be charged, incompressible, nonpolarizable spheres. 2. Ions try to surround themselves with as many ions of opposite charge as closely as possible. Usually in the packing arrangement, the cation is just large enough to allow te anions to surround it without touching one another. 3. The cation to anion ratio must reflect the stoichiometry of the compound. For MgCl2 the lattice must be an array of chloride anions with only half that number of magnesium ion.
An ionic lattice is a structure of millions of atomic formations of an ionic substance, structured like building blocks into one three-dimensional formation.
A chemical bond is a mutual attraction between the nuclei and valence electrons of two different atoms. This attraction results in the two atoms binding together. An ionic bond, also called an electron-transfer bond, is a type of chemical bond that is a result of the electromagnetic attraction between ions of opposite charges, i.e., a cation (a positively charged ion) and an anion (a negatively charged ion). An ion is an atom or group of atoms that has acquired an electrical charge due to the loss or gain of electrons. In an ionic bond, an atom gives or receives electrons from another atom. This is in contrast to covalent bonding, where two atoms share electron pairs between them. An ionic compound consists of anions and cations combined such that the total charge of the molecule is zero. All salts are ionic compounds.
One characteristic that both ionic and covalent compounds share is that they adhere to the octet rule. The octet rule is the principle that describes the bonding in atoms. Individual atoms are unstable unless they have an octet of electrons in their highest energy level.