«Մասնակից:Արսենյան Գոհար/Ավազարկղ»–ի խմբագրումների տարբերություն

One of the main characteristics of a molecule is its geometry often called its [[molecular structure|structure]]. While the structure of diatomic, triatomic or tetra-atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.

 

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| data1 = [[File:Cín.png|100px]] [[File:Sulfur-sample.jpg|100px]]

A chemical substance is a kind of matter with a definite [[chemical composition|composition]] and set of [[chemical properties|properties]].<ref>{{Cite book| title = General Chemistry |author1=Hill, J.W. |author2=Petrucci, R.H. |author3=McCreary, T.W. |author4=Perry, S.S. | edition = 4th | publisher = Pearson Prentice Hall | location = Upper Saddle River, New Jersey | year = 2005 | page = 37}}</ref> A collection of substances is called a mixture. Examples of mixtures are [[Earth's atmosphere|air]] and [[alloy]]s.<ref>{{cite book|title=Magnesium and Magnesium Alloys|page=59|author1=M.M. Avedesian|author2=Hugh Baker|publisher=ASM International}}</ref>

 

{{Main|Mole (unit)|l1=Mole}}

The mole is a unit of measurement that denotes an [[amount of substance]] (also called chemical amount). The mole is defined as the number of atoms found in exactly 0.012 kilogram (or 12&nbsp;grams) of [[carbon-12]], where the carbon-12 atoms are unbound, at rest and in their [[ground state]].<ref>{{cite web|url=http://www.bipm.org/en/si/base_units/ |title=Official SI Unit definitions |publisher=Bipm.org |accessdate=2011-06-12}}</ref> The number of entities per mole is known as the [[Avogadro constant]], and is determined empirically to be approximately 6.022{{e|23}} mol⁻¹.{{sfn|Burrows|Holman|Parsons|Pilling|2008|p=16}} [[Molar concentration]] is the amount of a particular substance per volume of [[solution]], and is commonly reported in mol/[[decimetre|dm]]³.{{sfn|Atkins|de Paula|2009|p=9}}

 

[[File:Phase changes.svg|thumb|upright=1.25|Diagram showing relationships among the phases and the terms used to describe phase changes.]]

{{Main|Phase (matter)|l1=Phase}}

A reductant transfers electrons to another substance and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Oxidation and reduction properly refer to a change in oxidation number—the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in [[oxidation number]], and reduction as a decrease in oxidation number.

 

 

Although the concept of [[Chemical equilibrium|equilibrium]] is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible, as for example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase.

{{Main|History of chemistry}}

The [[history of chemistry]] spans a period from very old times to the present. Since several millennia BC, civilizations were using technologies that would eventually form the basis of the various branches of chemistry. Examples include extracting [[metal]]s from [[ore]]s, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into [[soap]], making [[glass]], and making [[alloy]]s like [[bronze]]. Chemistry was preceded by its protoscience, [[alchemy]], which is an intuitive but non-scientific approach to understanding the constituents of matter and their interactions. It was unsuccessful in explaining the nature of matter and its transformations, but, by performing experiments and recording the results, alchemists set the stage for modern chemistry. Chemistry as a body of knowledge distinct from alchemy began to emerge when a clear differentiation was made between them by [[Robert Boyle]] in his work ''[[The Sceptical Chymist]]'' (1661). While both alchemy and chemistry are concerned with matter and its transformations, the crucial difference was given by the [[scientific method]] that [[chemist]]s employed in their work. Chemistry is considered to have become an established science with the work of [[Antoine Lavoisier]], who developed a law of [[conservation of mass]] that demanded careful measurement and quantitative observations of chemical phenomena. The history of chemistry is intertwined with the [[history of thermodynamics]], especially through the work of [[Willard Gibbs]].<ref>[http://web.lemoyne.edu/~giunta/papers.html Selected Classic Papers from the History of Chemistry]</ref>

The definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term "chymistry", in the view of noted scientist [[Robert Boyle]] in 1661, meant the subject of the material principles of mixed bodies.<ref>{{Cite book| last=Boyle | first = Robert |title =The Sceptical Chymist|location=New York | publisher=Dover Publications, Inc. (reprint)|year=1661|isbn=978-0-486-42825-3}}</ref> In 1663, the chemist [[Christopher Glaser]] described "chymistry" as a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection.<ref>{{Cite book| last=Glaser | first = Christopher |title= Traite de la chymie|location=Paris | year=1663}} as found in: {{Cite book| last = Kim | first = Mi Gyung | title = Affinity, That Elusive Dream – A Genealogy of the Chemical Revolution | publisher = The MIT Press | year = 2003 | isbn = 978-0-262-11273-4}}

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