Identify the following compounds as polar covalent, nonpolar covalent, or ionic?

Look at the electronegativity difference for each molecule. You will need an electronegativity chart to do so. If the difference is less than 0.6, it is just covalent. If it is between 0.6 and 2.1, it is polar covalent. Anything above 2.1 is ionic. For example, the eletronegativity of Na is 0.9 and the e of I is 2.5; thus I2.5-0.9I = 1.6 so the molecule NaI is polar covalent.