The Mole

The Mole:
A single atom or a few atoms are rarely encountered.  Instead, larger, macroscopic quantities
are used to quantify or measure collections of atoms or molecules, such as a glass of water, a
gallon of alcohol, or two aspirin.  Chemists have introduced a large unit of matter, the mole, to
deal with macroscopic samples of matter. 
One mole represents a definite number of objects, substances, or particles. For example, a mole
of atoms, a mole of ions, a mole of molecules. A mole is defined as the quantity of a pure substance that contains 6.022 x 10^23 units of that substance.  In other words, a mole is Avogadro's number of anything.