A mole is a universal unit used to measure the amount of a certain chemical. Using grams or absolute numbers of atoms/molecules/ions would be way too confusing. Thus, a mole makes it easier to know how much of a certain chemical there is. The mole today is widely credited to the discovery of Avogadro's number, the number of particles in one mole of any substance. Italian physicist, Amedeo Avogadro, was a lawyer, but later got interested in physics and became a scientist. Avogadro was the first person to propose the idea of molecules. He based much his work on the earlier discovery by Joseph Gay-Lussac that gases combine with each other in simple, whole-number ratios of volumes. For example, one liter of oxygen combines with two liters of hydrogen to make two liters of water vapor. Avogadro argued that this discovery could be proved if it was assumed one liter of gas contained the same amount of particles as any other liter of gas. The next question that arose was, "Then how many particles are in one liter of gas?" Avogadro never devoted significant time to answering this question. In 1865, for example, the German physicist J. Loschmidt estimated the number of molecules in a liter of gas to be 2.7 × 10^22. The accepted value today is 6.02 x 10^23.
As stated earlier, moles are important to chemistry because they provide a means for measuring the amounts of a certain chemical in a logical and universal manner. In a chemical reaction, moles can be used to determine the amount of a certain chemical needed or the amount that will be produced. There is 1 mole of atoms in the atomic mass of an element when that mass is expressed in grams. Given the mass of a an element in grams, division by the molar mass of the element to get the total moles. Given the particles of an element, it takes division by Avogadro's number to get the amount of moles.
Information collected from the following sources:
http://www.scientificamerican.com/article.cfm?id=how-was-avogadros-number
http://science.jrank.org/pages/697/Avogadro-s-Number.html
http://web.vu.union.edu/~stodolan/mole.html
http://www.chemistry.co.nz/avogadro.htm
