Background:
Imagine trying to purchase fruit without being able to count the number or measure the mass of the pieces you choose. Sounds difficult, doesn’t it? Every day people perform a variety of tasks that require the ability to count or measure. In some cases, the job is easier than in others – but it is always important.
Counting atoms, like counting sand particles, is no easy task! Perhaps you are wondering if it is even possible, considering how very small atoms are. The answer is yes, but you do not count the number of atoms as you might count marbles in a box. Over the past 50 years, scientists have devised many direct and indirect methods for determining this number using sophisticated equipment. To find the number of atoms in a given mass of an element, chemists decided to use the element carbon as a standard. The number of atoms in 12.0 grams of carbon-12 was determined experimentally. From such experiments, it was found that the number of atoms of an element whose mass in grams is numerically equal to its atomic mass is 6.02 x 1023. This number is Avogadro’s number.
The mole establishes a relationship between the atomic mass unit and the gram. The mole might seem to be a strange term, but the concept is not. Every day you encounter many items that are usually packaged together and described as a group. Like dozen, gross, or ream, it is convenient to have a special name to describe a group of atoms. The group in chemistry is the mole, and it contains 6.02 x 1023 items.