PS-4.4   Classify compounds as crystalline (containing ionic bonds) or molecular (containing covalent bonds) based on whether their outer electrons are transferred or shared
Key Concepts:
Ionic bonds: electron transfer, ions
Covalent bonds: shared electrons
  As stated previously, in PS-4.3, Ionic compounds form formula units and are crystalline in nature. They exist a a crystal lattice with a size that is only limited by the number of formula units that are available to cluster together in a pattern that will cancel the net charge of the ions. However, when nonmetals form compounds with other nonmetals to produce a stable product, they form covalent bonds. When atoms are covalently bonded, that is, they share valence electrons to bond, the result is a molecule that has a finite ( fixed) size. Remember:
1. Nonmetals will share electrons with each other.
2. Bonds formed by sharing electrons are covalent bonds.
3. Compounds that have covalent bonds are molecules.