Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto (,
also , ; 9 August 17769 July 1856) was an
Italian scientist
A scientist is a person who conducts scientific research to advance knowledge in an area of the natural sciences.
In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosophica ...
, most noted for his contribution to
molecular theory
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...
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 ratio of the number of elementary entities (
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas ...
s,
molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...
s,
ions or other particles) in a substance to its
amount of substance
In chemistry, the amount of substance ''n'' in a given sample of matter is defined as the quantity or number of discrete atomic-scale particles in it divided by the Avogadro constant ''N''A. The particles or entities may be molecules, atoms, io ...
(the latter having the unit
mole), , is known as the
Avogadro constant
The Avogadro constant, commonly denoted or , is the proportionality factor that relates the number of constituent particles (usually molecules, atoms or ions) in a sample with the amount of substance in that sample. It is an SI defining con ...
. This constant is denoted ''N''
A, and is one of the seven defining constants of the
SI.
Biography
Amedeo Avogadro was born in
Turin
Turin ( , Piedmontese: ; it, Torino ) is a city and an important business and cultural centre in Northern Italy. It is the capital city of Piedmont and of the Metropolitan City of Turin, and was the first Italian capital from 1861 to 1865. Th ...
to a noble family of the
Kingdom of Sardinia
The Kingdom of Sardinia,The name of the state was originally Latin: , or when the kingdom was still considered to include Corsica. In Italian it is , in French , in Sardinian , and in Piedmontese . also referred to as the Kingdom of Savoy-S ...
(now part of
Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
) in the year 1776. He graduated in
ecclesiastical law
Canon law (from grc, κανών, , a 'straight measuring rod, ruler') is a set of ordinances and regulations made by ecclesiastical authority (church leadership) for the government of a Christian organization or church and its members. It is th ...
at the late age of 20 and began to practice. Soon after, he dedicated himself to
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which rel ...
and
mathematics (then called ''positive philosophy''),
and in 1809 started teaching them at a ''liceo'' (high school) in
Vercelli
Vercelli (; pms, Vërsèj ), is a city and ''comune'' of 46,552 inhabitants (January 1, 2017) in the Province of Vercelli, Piedmont, northern Italy. One of the oldest urban sites in northern Italy, it was founded, according to most historians, ...
, 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'' ("Essay on a manner of Determining the Relative Masses of the Elementary Molecules of Bodies and the Proportions by Which They Enter These Combinations"), which contains Avogadro's hypothesis. Avogadro submitted this essay to
Jean-Claude Delamétherie's ''Journal de Physique, de Chimie et d'Histoire naturelle'' ("Journal of Physics, Chemistry and Natural History").
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
The Kingdom of Sardinia,The name of the state was originally Latin: , or when the kingdom was still considered to include Corsica. In Italian it is , in French , in Sardinian , and in Piedmontese . also referred to as the Kingdom of Savoy-S ...
under
Victor Emmanuel I. Avogadro was active in the
revolutionary movement of March 1821. As a result, he lost his chair in 1823 (or, as the university officially declared, it was "very glad to allow this interesting scientist to take a rest from heavy teaching duties, in order to be able to give better attention to his researches"). Eventually, King
Charles Albert granted a Constitution (''
Statuto Albertino
The Statuto Albertino (English language, English: ''Albertine Statute'') was the constitution granted by King Charles Albert of Sardinia to the Kingdom of Sardinia on 4 March 1848 and written in Italian and French. The Statute later became the ...
'') 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 (he introduced the
metric system
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Intern ...
into Piedmont) 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
The Avogadro constant, commonly denoted or , is the proportionality factor that relates the number of constituent particles (usually molecules, atoms or ions) in a sample with the amount of substance in that sample. It is an SI defining con ...
, ''N''
A. 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 (
Loschmidt constant
The ''Loschmidt constant'' or Loschmidt's number (symbol: ''n''0) is the number of particles (atoms or molecules) of an ideal gas in a given volume (the number density), and usually quoted at standard temperature and pressure. The 2014 CODATA rec ...
now has another meaning).
Avogadro's law states that the relationship between the masses of the same volume of all gases (at the same temperature and pressure) 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
Joseph Louis Gay-Lussac (, , ; 6 December 1778 – 9 May 1850) was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen (with Alexander von Humboldt), for two laws ...
published his law on volumes (and combining gases) 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. (For instance,
John Dalton
John Dalton (; 5 or 6 September 1766 – 27 July 1844) was an English chemist, physicist and meteorologist. He is best known for introducing the atomic theory into chemistry, and for his research into colour blindness, which he had. Colour b ...
did not consider this possibility.) 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" (our "atom"). Also, he gave more attention to the definition of
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different element ...
, as distinguished from
weight
In science and engineering, the weight of an object is the force acting on the object due to gravity.
Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object. Others define weight as a scalar q ...
.
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'' ("Note on the Relative Masses of Elementary Molecules, or Suggested Densities of Their Gases, and on the Constituents of Some of Their Compounds, As a Follow-up to the Essay on the Same Subject, Published in the Journal of Physics, July 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'' (''New Considerations on the Theory of Proportions Determined in Combinations, and on Determination of the Masses of Atoms'') and shortly afterwards, ''Mémoire sur la manière de ramener les composès organiques aux lois ordinaires des proportions déterminées'' ("Note on the Manner of Finding the Organic Composition by the Ordinary Laws of Determined Proportions").
In 1841, he published his work in ''Fisica 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
André-Marie Ampère (, ; ; 20 January 177510 June 1836) was a French physicist and mathematician who was one of the founders of the science of classical electromagnetism, which he referred to as "electrodynamics". He is also the inventor of n ...
proposed a very similar theory three years later (in his '; "On the Determination of Proportions in which Bodies Combine According to the Number and the Respective Disposition of the Molecules by Which Their Integral Particles Are Made"), but the same indifference was shown to his theory as well.
Only through studies by
Charles Frédéric Gerhardt and
Auguste Laurent
Auguste Laurent (14 November 1807 – 15 April 1853) was a French chemist who helped in the founding of organic chemistry with his discoveries of anthracene, phthalic acid, and carbolic acid.
He devised a systematic nomenclature for organic chem ...
on
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clay ...
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
The name Victor or Viktor may refer to:
* Victor (name), including a list of people with the given name, mononym, or surname
Arts and entertainment
Film
* ''Victor'' (1951 film), a French drama film
* ''Victor'' (1993 film), a French shor ...
attended, and Avogadro's great contribution to chemistry was recognized.
Rudolf Clausius
Rudolf Julius Emanuel Clausius (; 2 January 1822 – 24 August 1888) was a German physicist and mathematician and is considered one of the central founding fathers of the science of thermodynamics. By his restatement of Sadi Carnot's principle ...
, 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.
See also
*
Avogadrite
Avogadrite ((K,Cs)BF4) is a potassium- caesium tetrafluoroborate in the halide class. Avogadrite crystallizes in the orthorhombic system (space group ''Pnma'') with cell parameters ''a'' 8.66 Å, ''b'' 5.48 Å and ''c'' Å 7.03.
History
The min ...
(mineral)
*
Avogadro (
lunar crater
Lunar craters are impact craters on Earth's Moon. The Moon's surface has many craters, all of which were formed by impacts. The International Astronomical Union currently recognizes 9,137 craters, of which 1,675 have been dated.
History
The wor ...
)
References
Further reading
*
*
*
* Morselli, Mario. (1984). ''Amedeo Avogadro, a Scientific Biography.'' Kluwer. .
** Review of Morselli's book:
* Pierre Radvanyi, "Two hypothesis of Avogadro", 1811 Avogadro's article analyzed on
BibNum' (click 'Télécharger').
External links
*
{{DEFAULTSORT:Avogadro, Amedeo
1776 births
1856 deaths
Scientists from Turin
Italian chemists
Fluid dynamicists
People from the Kingdom of Sardinia
University of Turin faculty