8.2. Ionic Bonds and Ionic Compounds http://www.ck12.org
Crystal Lattices
Any ionic compound is composed of extremely large numbers of cations and anions. Each cation is attracted by
all of the anions but repelled by all the other cations, and vice versa. In order to maximize the number of attractive
interactions while minimizing the repulsive ones, the ions form a three-dimensional structure known as acrystal
lattice. There are a variety of lattice forms that ionic compounds can exhibit, but all of them involve a regular,
repeating pattern in which cations and anions are held rigidly in place by various neighboring ions. For example,
sodium fluoride takes the form of a cubic lattice, shown here (Figure8.6):
FIGURE 8.6
Crystal Lattice for Sodium FluorideSome properties of the crystal form that are exhibited at the atomic level can also be seen at the macroscopic level.
Due to the cubic arrangement of ions in sodium fluoride, a single pure crystal of this compound will tend to have
smooth faces at right angles to one another (Figure8.7).
FIGURE 8.7
Crystals of Villiaumite, a rare mineral
composed of sodium fluoride.