Bonding Clues: Electrolytes and Nonelectrolytes

Scientists can get some good clues about the type of bonding in a compound by discovering whether a substance is an electrolyte or a nonelectrolyte. Ionically bonded substances act as electrolytes, but covalently bonded compounds, in which no ions are present, are commonly nonelectrolytes. Electrolytes are substances that conduct electricity in the molten state or when dissolved in water. For instance, sodium chloride is an electrolyte because it conducts an electrical current when dissolved in water. If you were to melt pure NaCl (which requires a lot of heat!) and then check the conductivity of the molten salt, you’d find that the molten table salt also conducts electricity. In the molten state, the NaCl ions are free to move and carry electrons, just as they are in the saltwater solution.

Substances that don’t conduct electricity when in these states are called nonelectrolytes. Table sugar, or sucrose, is a good example of a nonelectrolyte. You can dissolve sugar in water or melt it, but it won’t have conductivity. No ions are present to transfer the electrons.