Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto, was an Italianscientist, most noted for his contribution to molecular theory now known as Avogadro's law, which states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of molecules. In tribute to him, the number of elementary entities in 1 mole of a substance,, is known as the Avogadro constant, one of the seven SI base units and represented by NA.
Biography
Amedeo Avogadro was born in Turin to a noble family of the Kingdom of Sardinia in the year 1776. He graduated in ecclesiastical law at the late age of 20 and began to practice. Soon after, he dedicated himself to physics and mathematics, and in 1809 started teaching them at a liceo in Vercelli, where his family lived and had some property. In 1811, he published an article with the title Essai d'une manière de déterminer les masses relatives des molécules élémentaires des corps, et les proportions selon lesquelles elles entrent dans ces combinaisons, which contains Avogadro's hypothesis. Avogadro submitted this essay to Jean-Claude Delamétherie's Journal de Physique, de Chimie et d'Histoire naturelle. In 1820, he became a professor of physics at the University of Turin. Turin was now the capital of the restored Savoyard Kingdom of Sardinia under Victor Emmanuel I. Avogadro was active in the revolutionary movement of March 1821. As a result, he lost his chair in 1823. Eventually, King Charles Albert granted a Constitution in 1848. Well before this, Avogadro had been recalled to the university in Turin in 1833, where he taught for another twenty years. Little is known about Avogadro's private life, which appears to have been sober and religious. He married Felicita Mazzé and had six children. Avogadro held posts dealing with statistics, meteorology, and weights and measures and was a member of the Royal Superior Council on Public Instruction. He died on 9 July 1856.
Accomplishments
In honor of Avogadro's contributions to molecular theory, the number of molecules per mole of substance is named the "Avogadro constant", NA. It is exactly The Avogadro constant is used to compute the results of chemical reactions. It allows chemists to determine the amounts of substances produced in a given reaction to a great degree of accuracy. Johann Josef Loschmidt first calculated the value of the Avogadro constant, the number of particles in one mole, sometimes referred to as the Loschmidt number in German-speaking countries. Avogadro's Law states that the relationship between the masses of the same volume of all gases corresponds to the relationship between their respective molecular weights. Hence, the relative molecular mass of a gas can be calculated from the mass of a sample of known volume. Avogadro developed this hypothesis after Joseph Louis Gay-Lussac published his law on volumes in 1808. The greatest problem Avogadro had to resolve was the confusion at that time regarding atoms and molecules. One of his most important contributions was clearly distinguishing one from the other, stating that gases are composed of molecules, and these molecules are composed of atoms. Avogadro did not actually use the word "atom" as the words "atom" and "molecule" were used almost without difference. He believed that there were three kinds of "molecules," including an "elementary molecule". Also, he gave more attention to the definition of mass, as distinguished from weight. In 1815, he published Mémoire sur les masses relatives des molécules des corps simples, ou densités présumées de leur gaz, et sur la constitution de quelques-uns de leur composés, pour servir de suite à l'Essai sur le même sujet, publié dans le Journal de Physique, juillet 1811 about gas densities. In 1821 he published another paper, Nouvelles considérations sur la théorie des proportions déterminées dans les combinaisons, et sur la détermination des masses des molécules des corps and shortly afterwards, Mémoire sur la manière de ramener les composès organiques aux lois ordinaires des proportions déterminées. In 1841, he published his work inFisica dei corpi ponderabili, ossia Trattato della costituzione materiale de' corpi, 4 volumes.
Response to the theory
The scientific community did not give great attention to Avogadro's theory, and it was not immediately accepted. André-Marie Ampère proposed a very similar theory three years later, but the same indifference was shown to his theory as well. Only through studies by Charles Frédéric Gerhardt and Auguste Laurent on organic chemistry was it possible to demonstrate that Avogadro's law explained why the same quantities of molecules in a gas have the same volume. Unfortunately, related experiments with some inorganic substances showed seeming contradictions. This was finally resolved by Stanislao Cannizzaro, as announced at Karlsruhe Congress in 1860, four years after Avogadro's death. He explained that these exceptions were due to molecular dissociations at certain temperatures, and that Avogadro's law determined not only molecular masses, but atomic masses as well. In 1911, a meeting in Turin commemorated the hundredth anniversary of the publication of Avogadro's classic 1811 paper. King Victor Emmanuel III attended, and Avogadro's great contribution to chemistry was recognized. Rudolf Clausius, with his kinetic theory on gases proposed in 1857, provided further evidence for Avogadro's Law. Jacobus Henricus van 't Hoff showed that Avogadro's theory also held in dilute solutions. Avogadro is hailed as a founder of the atomic-molecular theory.
