Introduction
Lorenzo Amedeo Avogadro was born in 1776 in Turin city of Italy and died in 1856 at the age of 81 years after making a great positive contribution in the field of science especially chemistry. He schooled in Turin and having come from a family background of lawyers, his career was oriented towards law whereby at the age of 16 years he had already become a bachelor of jurisprudence and four years down this profession he had managed to get a doctorate in ecclesiastical law which he began to practice and latter in 1801 he received an appointment in the department of Eridano as the secretary to the prefecture.
Avogadro’s interest in natural philosophy
Along with his successful career in legal matters, Avogadro had a lot of interest in the field of natural philosophy which influenced him to pursue private studies in both physics and mathematics in the year 1800 whereby three years down studies he carried out scientific research on electricity together with his brother. In 1803 he was appointed to be a demonstrator at Turin academy which was followed by him becoming a professor of natural philosophy at Vercelli University in 1809.
Avogadro received another appointment to head the chair in mathematical physic when it was first established in Italy in1820 at the university of Turin an appointment which he did not hold for long because the political changes at that time suppressed the chair making him lose the job in1822 until 1832 when he was reinstated. (Mario, 2003)
Avogadro’s contribution to chemistry
In his article, journal de physique, which was published in 1811, Avogadro clearly described the distinction between an atom and a molecule which Dalton had failed to differentiate in his work in1808 and was confused between the two. Dalton assumed that in common compounds with two elements, each element contributed one atom. Dalton had considered particles to be the same as atoms and failed to admit that one oxygen particle could yield two particles of water.
It was Avogadro who made it clear that ‘’atoms’’ of hydrogen and oxygen are ”molecules” made up of two atoms each and therefore when two hydrogen molecules combine with one oxygen molecule, two water molecules are produced. Avogadro suggested that at the same conditions of pressure and temperature all gases with equal volumes contained an equal number of molecules which is the modern definition of Avogadro’s principle. This principle was the basis of determining the molar masses as well as atomic masses.
The Avogadro’s number
Avogadro’s number which is also known as Avogadro’s constant is the number of particles in one mole of any substance and its value is 6.0221367 x 1023. This number was not actually determined by Amedeo himself because he did not know about moles at this time or of any number that would later bear his name. It was through the work of Cannizzaro in 1860 that used the ideas of Avogadro to come up with the number and obtained sets of atomic weights which were based on oxygen with an atomic mass of 16.
Conclusion
Today our definition of mole determines the size of Avogadro’s number and this number demonstrates the small size of both atoms and molecules in comparison with the number of substances we are aware of in our daily life. For example, we define a mole of a substance as the amount of the substance which contains as many particles as there are carbon atoms in12 grams of the carbon-12 isotope. (Mario, 2003)
References
Mario M. (2003): Amedeo Avogadro: Hardcover publishers.