Ionic Bonds
An ionic bond is a chemical bond between a nonmetal ion and a metal ion of opposite charges. Ionic bonds are formed when the metal ion donates one or more electrons to the nonmetal ion, and their opposite charges attract one another to form a bond.
The combination of an anion and a cation forms an ion, where an ion of a single atom is called a monatomic ion and an ion of two or more atoms is called a polyatomic ion.
The charges of an ion are indicated with a “+” or “-” and are shown in the chemical formula of the ion. An ion of “X+” where X is a number, means the ion has X less electrons., and an ion of “X-” means the ion has an excess of X electrons.
You can tell what kind of bonding you have based on the differences in electronegativity: >0.5 is covalent, 0.5<x<1.7 is polar covalent, and >1.7 is ionic.
Crystal Lattices
Ionic solids are formed when ions are packed together into a crystal lattice. The crystal lattice is a repeating network of anions and cations. Ionic solids are hard and brittle, and have high boiling points.
Here is a series of digital paintings
showing the formation of a crystal lattice:
There is one host atom ("lattice point") at each corner of a cubic unit cell.
There is one host atom at each corner of the cubic unit cell and one atom in the cell center.
There is one host atom at each corner, one host atom in each face, and the host atoms touch along the face diagonal.
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