As discussed in Module 2, you can tell the difference between an ionic and covalent compound by looking for metals in the chemical formula. If there is a metal (left side of the jagged line on the periodic chart) in the compound, it is an ionic compound. If there are only non-metals (right side of the jagged line on the periodic chart), it is a covalent compound. NaNO₃, then, is ionic while NH₃ is covalent.

As discussed in Module 5, to determine whether or not a molecule is polar covalent or nonpolar covalent, you need to look at two things:

1. If there is only one element in the molecule (O₂, Br₂, O₃, etc.) then the molecule is purely covalent.

2. If there is more than one element in the molecule, the molecule has polar bonds, but may not be a polar covalent molecule. To determine whether or not it is polar, you must draw the Lewis structure and then determine the molecular geometry. If the molecular geometry allows the polar bonds to cancel out, such as in the linear geometry of CO₂ or the tetrahedral geometry of CH₄, then the molecule is nonpolar covalent. If the geometry does not allow the polar bonds to cancel, such as the pyramidal geometry of NH₃ or the bent geometry of H₂O, then the molecule us polar covalent.