The Mole

A microscopic view of a glass crystal

The study of chemistry is especially challenging because of the unbelievably small particles which compose matter. The direct study of atoms and molecules is impossible without modern technology only available to top-notch research laboratories. Fortunately, chemicals react in predictable ways based on their electronegativity values and their ionization energies. This allows chemists to predict and explain the qualitative behavior of matter, but what about the quantitative nature? Understanding the quantitative relationships of matter requires understanding the concept of the mole. Since atoms are so small, it requires a large number of them to become observable by the naked eye.

Based on the mass of carbon-12, scientists developed what is known as Avogadro's number. One mole of carbon-12 weighs exactly 12 grams and contains 6.02x1023 atoms of carbon.  Chemicals react in predictable quantitative relationships and scientists use the mole as a packaging unit for matter.

Essential Question

• Why is the mole used as a unit of measure in chemistry?