History on Avogadro’s Number
Lorenzo Romano Amedeo Carlo Avogadro was born in Turin, Italy, on 9th August, 1776. His family was very wealthy and popular among the people. Even though Avogadro’s family was mostly lawyers, he enjoyed private studies of mathematics and physics. His first scientific research in 1803 was on electricity.
After John Dalton published his New System of Chemical Philosophy, more and more additions to the knowledge of chemistry were revealed. In 1811, Avogadro published an article in Journal de physique that clearly drew the distinction between the molecule and the atom. He pointed out that Dalton had confused the concepts of atoms and molecules. The "atoms" of nitrogen and oxygen are in reality "molecules" containing two atoms each. Thus two molecules of hydrogen can combine with one molecule of oxygen to produce two molecules of water. Avogadro suggested that equal volumes of all gases at the same temperature and pressure contain the same number of molecules.
It was long after Avogadro died that the idea of a mole was introduced. Since a molecular weight in grams (mole) of any substance contains the same number of molecules, then according to Avogadro's Principle, the molar volumes of all gases should be the same. The number of molecules in one mole is now called Avogadro's number. Avogadro had no knowledge of moles or of the number that concord with his name. The number was never determined by Avogadro himself. Avogadro's number is very large, and the presently accepted value is 6.0221367 x 1023.
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