Avogadro, Amedeo Cannizzaro

The idea of chemical equivalents was stated by Henry Cavendish in 1767, clarified by Jeremias Richter in 1795, and popularized by William Wollaston in 1814. Wollaston applied the concept to elements and defined it in such a way that one equivalent of an element corresponded to its atomic mass. Thus, when Wollaston s equivalent is expressed in grams, it is identical to a mole. It is not surprising then that the word mole is derived from molekulargewicht (German, meaning molecular weight ) and was coined in 1901 or 1902. see ALSO Avogadro, Amedeo Cannizzaro, Stanislao Cavendish, Henry Gay-Lussac, Joseph-Louis. 

Ostwald s reluctance to accept the chemical atom as an entity would surely have yielded to the overwhelming evidence provided by scanning tunneling microscopy (STM). Although Ostwald did not hve to see it, this technique provides such clear evidence of the reality of simple atoms that even he would have been convinced, see also Avogadro, Amedeo Berthol-let, Claude-Louis Berzehus, JonsJaKob Boyle, Robert Cannizzaro, Stanislao Dalton, John Einstein, Albert Gay-Lussac, Joseph-Louis Lavoisier, Antoine Ostwald, Eriedrich Wilhelm Svedberg, Theodor Molecules. 

The electronic and molecular geometries of covalent molecules, and hence their resulting polarities, can thus be predicted fairly accurately. Armed with these tools, one can predict whether or not a molecule should be soluble, reactive, or even toxic, see also Bonding Avogadro, Amedeo Bohr, Niels Cannizzaro, Stanislao Dalton, John Le Bel, Joseph-Achille Lewis, Gilbert N. Lewis Structures Pauling, Linus Thomson, Joseph John van t Hoff, Jacobus. 

For nearly three centuries, a new element has been discovered every two-and-one-half years, on average. Undoubtedly, more will be found. Although their names and their discoveries will fikely involve controversies, their place at the table is already set. see also Alchemy Avogadro, Amedeo Bec-QUEREL, Antoine-Henri Bohr, Niels Cannizzaro, Stanislao Dalton, John Lavoisier, TVntoine Mendeleev, Dimitri Meyer, Lothar Pauli, Wolfgang Ramsay, William Rontgen, Wilhelm Rutherford, Ernest Seaborg, Glenn Theodore Thomson, Joseph John. 

Avogadro, Amedeo (1776-1856) Italian chemist and physicist, in 1811 he published his hypothesis (seeAvoGADRo s law), which provided a method of calculating molecular weights from vapour densities. The importance of the work remained unrecognized, however, until championed by Stanislao Cannizzaro (1826-1910) in 1860. 

In 1860 Stanislao Cannizzaro (Hshowed that the earlier hypothesis of Amedeo Avogadro (1811, ii... 

One of the key components of such a scheme was provided in I860 by the Italian chemist Stanislao Cannizzaro, who announced at an international chemical conference in Karlsruhe that the work of his compatriot Amedeo Avogadro provided an improved list of the atomic weights of the elements. This list allowed an accurate ranking of the elements by weight, from the lightest (hydrogen) to the heaviest. 

Cannizzaro was a talented organic chemist and an early leader in the discipline, but it is his contribution to the then-existing debate over atoms, molecules, and atomic weights for which he is best known. He championed Amedeo Avogadro s notion that equal volumes of gas at the same pressure and temperature held equal numbers of molecules or atoms, and the notion that equal volumes of gas could be used to calculate atomic weights. In so doing, Cannizzaro provided a new understanding of chemistry. 

Mendeleev also attended the 1860 Karlsruhe Congress, the first international chemistry conference. Many of the leading chemists of the day were in attendance, and one of the central questions addressed was the appropriate method for calculating atomic weight. Different chemists used different systems, leading to widespread confusion over everything from nomenclature to chemical formulas. Mendeleev heard the Itafian chemist Stanislao Cannizzaro present Amedeo Avogadro s hypothesis that equal vol-tunes of gas under equal temperature and pressure contained equal numbers of molecules. 

Cannizzaro, Stanislao (1826-1910) Italian chemist. Cannizzaro was responsible for reviving interest in the ideas of Amedeo avogadro in a pamphlet published in 1858 and in an address to the Chemical Congress at Karlsruhe, Germany. His pamphlet clarified the concepts of atomic and molecular weights and also showed how the molecular weight (now termed relative molecular mass) of a compound could be determined by measuring its vapor density. He also discovered the... 

In 1738 Daniel Bernoulli proposed a concept of gas behavior based on the assumption that gases are composed of invisibly small, separated particles called MOLECULES. The idea that the volume of a gas depends on the number of molecules it contains was vaguely conceived by scientists as early as about 1760. The first clear statement of this relationship was made by Amedeo Avogadro in 1811, but it was not fully accepted until the later work of Cannizzaro, about 1860. In modem terms, it says, equal volumes of all gases at the same temperature and pressure contain the same number of molecules." Expressed as an equation, where N is the number of molecules, Avogadro s law is... 

Avogadro s law A law that states that equal volumes of gases at the same temperature and pressure contain the same number of molecules. This was first stated as a hypothesis by the Italian chemist and physicist Amedeo Avogadro (1776-1856) in 1811. However, this law was not generally accepted until after his death when the Italian chemist Stanislao Cannizzaro was able to explain why there were some exceptions to the hypothesis. 

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