The Italian scientist, Amedeo Avogadro, is most famous for his contributions to the theory of moles and molecular weight, including what is known as Avogadro’s law. In respect of his contributions to the molecular theory, the number of molecules in one mole was renamed Avogadro’s number.
Amedeo was born in Turin, Italy, on 9th August, 1776 in a noble family of lawyers. His father, Count Filippo Avogadro, was a well-known lawyer and civil servant. Amedeo followed his father’s footsteps and earned a doctorate of law in 1796 and began to practise. Soon after, he developed interest in natural philosophy and mathematics. Despite his successful legal career, he left it to teach mathematics and physics at liceo (high school) in Vercelli in 1809.
In 1820, he was appointed as the professor of mathematical physics at the University of Turin. Unluckily, his post was short-lived, since political turmoil suppressed the chair and Avogadro lost his job by July, 1822. The post was however reestablished in 1832, and Avogadro took his position back in 1834. Here, he remained until his retirement in 1850.
Not much is known about Amedeo’s private life and his political activity; despite his unpleasant aspect (at least as depicted in the rare images found), he was known to be dedicated to a sober life and a religious man. He was happily married and blessed with six sons.
In 1811, Avogadro theorized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. He further established that relative molecular weights of any two gases are similar to the ratio of the densities of the two gases under the constant conditions of temperature and pressure. His suggestion is now known as the Avogadro’s principle. He also cleverly reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of two or more atoms. (Avogadro did not actually use the word atom; at the time the words atom and molecule were used almost interchangeably. He talked about three kinds of “molecules,” including an “elementary molecule”-what we would call an atom.) Thus Avogadro was able to resolve the confusion that Dalton and others had encountered regarding atoms and molecules at that time.
Avogadro’s findings were almost completely neglected until it was forcefully presented by Stanislao Cannizarro at the Karlsruhe Conference in 1860. He demonstrated that Avogadro’s Principle was not only helpful to determine molar masses, but also, indirectly, atomic masses. Avogadro’s work was mainly rejected before due to earlier established conviction that chemical combination occurred due to the similarity between unlike elements. After the electrical discoveries of Galvani and Volta, this similarity was in general attributed to the attraction between unlike charges.
The number of molecules in one mole is now called Avogadro’s number taking the value of 6.0221367 x 1023. The number was not actually determined by Avogadro himself. It was given his name due to his outstanding contribution to the development of molecular theory. This Italian scientist died on July 9th, 1856 in Turin.
