Allotropy is the property of some chemical elements to be able to take two or more different forms, where the atoms are arranged differently by chemical bonds. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic The forms are known as allotropes of that element. [1] The phenomenon of allotropy is sometimes also called allotropism. For example, carbon has two common allotropes: diamond, where the carbon atoms are bonded together in a tetrahedral lattice arrangement, and graphite, where the carbon atoms are bonded together in sheets of a hexagonal lattice. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in A tetrahedron (plural tetrahedra) is a Polyhedron composed of four triangular faces three of which meet at each vertex. The Mineral graphite, as with Diamond and Fullerene, is one of the Allotropes of carbon.
The word allotropy comes from the Greek allos, meaning "other", and tropos, "manner". Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly
Allotropy refers only to different forms of an element within the same phase or state of matter (i. A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter e. different solid, liquid or gas forms). A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of This page is about the physical properties of gas as a state of matter Changes of state (between solid, liquid and gas) are not considered allotropy. Some elements have allotropes that persist in different phases - for example, the two allotropes of oxygen (dioxygen, O2, and ozone, O3), can both exist in the solid, liquid and gaseous states. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the OZONE is an object oriented Operating system written in the C programming language. Other elements maintain distinct allotropes only in some phases - for example phosphorus has many solid allotropes, which all revert to the same P4 form when melted to the liquid state. Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15
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History
The concept of allotropy was originally proposed in 1841 by the Swedish scientist Baron Jons Jakob Berzelius (1779-1848) who offered no explanation. Friherre Jöns Jacob Berzelius (20 August 1779 &ndash 7 August 1848 was a Swedish chemist [2] After the acceptance of Avogadro's hypothesis in 1860 it was understood that elements could exist as polyatomic molecules, and the two allotropes of oxygen were recognized as O2 and O3. Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto, Count of Quaregna and Cerreto was an Italian Savant. In the early 20th century it was recognized that other cases such as carbon were due to differences in crystal structure.
By 1912, Ostwald noted that the allotropy of elements is just a special case of the phenomenon of polymorphism known for compounds, and proposed that the terms allotrope and allotropy be abandoned and replaced by polymorph and polymorphism. Friedrich Wilhelm Ostwald ( Latvian: Vilhelms Ostvalds; September 2, 1853 &ndash April 4, 1932) was a Baltic Polymorphism in Materials science is the ability of a solid material to exist in more than one form or Crystal structure Although many other chemists have repeated this advice, IUPAC and most chemistry texts still favour the usage of allotrope and allotropy for elements only. The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization
Differences in properties of an element's allotropes
Allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviours. The change between allotropic forms is triggered by the same forces that affect other structures, i. e. pressure, light, and temperature. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Therefore the stability of the particular allotropes depends on particular conditions. For instance, iron changes from a body-centered cubic structure (ferrite) to a face-centered cubic structure (austenite) above 906 °C, and tin undergoes a transformation known as tin pest from a metallic phase to a semiconductor phase below 13. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 The cubic crystal system (or isometric) is a Crystal system where the Unit cell is in the shape of a Cube. Ferrite or alpha iron ( α-Fe) is a Materials science term for Iron, or a Solid solution with iron as the main constituent with a The cubic crystal system (or isometric) is a Crystal system where the Unit cell is in the shape of a Cube. Austenite (or gamma phase iron is a metallic non-magnetic solid solution of Iron and an Alloying element Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 Tin pest is an autocatalytic, allotropic transformation of the element Tin, which causes deterioration of tin objects at low temperatures The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that 2 °C.
List of allotropes
Typically, elements capable of variable coordination number and/or oxidation states tend to exhibit greater numbers of allotropic forms. The coordination number of an atom in a molecule or a crystal is the number of its nearest neighbours In Chemistry, the oxidation state is an indicator of the degree of Oxidation of an Atom in a Chemical compound. Another contributing factor is the ability of an element to catenate. Catenation is the ability of a Chemical element usually found in carbon forming Covalent bonds with other Carbon atoms resulting in the formation of long Allotropes are typically more noticeable in non-metals and metalloids. Nonmetal is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties every element in the Metalloid is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties nearly every element Nevertheless, metals tend to have many allotropes. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across
Examples of allotropes include:
Non-metals
- diamond - an extremely hard, transparent crystal, with the carbon atoms arranged in a tetrahedral lattice. This is a list of the Allotropes of Carbon. Diamond See also Diamond Diamond is one of the best known allotropes In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in A poor electrical conductor. An excellent thermal conductor.
- graphite - a soft, black, flaky solid, a moderate electrical conductor. The Mineral graphite, as with Diamond and Fullerene, is one of the Allotropes of carbon. The C atoms are bonded in flat hexagonal lattices, which are then layered in sheets.
- amorphous carbon
- fullerenes, including "buckyballs", such as C60, and carbon nanotubes
- White phosphorus - crystalline solid P4
- Red phosphorus - polymeric solid
- Scarlet phosphorus
- Violet phosphorus
- Black phosphorus - semiconductor, analogous to graphite
- Diphosphorus
- dioxygen, O2 - colorless
- ozone, O3 - blue
- tetraoxygen, O4 - metastable
- octaoxygen, O8 - red
- dinitrogen
- tetranitrogen
- trinitrogen
- two solid forms: one hexagonal close-packed and the other alpha cubic
- Plastic (amorphous) sulfur - polymeric solid
- Rhombic sulfur - large crystals composed of S8 molecules
- Monoclinic sulfur - fine needle-like crystals
- Other ring molecules such as S7 and S12
- "Red selenium," cyclo-Se8
- Gray selenium, polymeric Se
- Black selenium
Metalloids
- amorphous boron - brown powder
- crystalline boron - black, hard (9. See also Activated carbon Amorphous carbon is an allotrope of carbon that does not have any Crystalline structure "C60" and "C-60" redirect here For other uses see C60 (disambiguation. "C60" and "C-60" redirect here For other uses see C60 (disambiguation. See also Graphene, Buckypaper Carbon nanotubes (CNTs are Allotropes of carbon with a nanostructure that can have a length-to-diameter Elemental Phosphorus can exist in several allotropes; the most common of which are white and red Diphosphorus, P2 is the Diatomic form of Phosphorus. Unlike its Nitrogen group neighbour Nitrogen which forms a stable N2 There are several known Allotropes of oxygen Dioxygen, O2 - colorless Ozone, O3 - blue Tetraoxygen OZONE is an object oriented Operating system written in the C programming language. O4 is also a subclass of O- class stars. The tetraoxygen molecule (O4 also called oxozone was first predicted in 1924 by Metastability is a general scientific concept which describes states of delicate equilibrium Solid oxygen forms at normal Atmospheric pressure at a temperature below 54 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 As reported in the January 18 2002 Edition of ''Science'' at the University of Rome La Sapienza, Fulvio Cacace and his colleagues created a novel form of nitrogen known as There are a large number of allotropes of Sulfur. In this respect sulfur is second only to carbon. Selenium (səˈliniəm is a Chemical element with the Atomic number 34 represented by the chemical symbol Se, an atomic mass of 78 Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B. 3 on Mohs' scale), and a weak conductor at room temperature.
- amorphous silicon - brown powder
- nanocrystalline silicon - similar to the amorphous silicon
- crystalline silicon - has a metallic luster and a grayish color. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Nanocrystalline silicon ( nc-Si)—an allotropic form of Silicon with Paracrystalline structure—is similar to Amorphous silicon Single crystals of crystalline silicon can be grown with a process known as the Czochralski process
- Yellow arsenic - molecular non-metallic As4
- Gray arsenic, polymeric As (metalloid)
- Black arsenic (metalloid) and several similar other ones. Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33
- blue-white antimony - the stable form (metalloid)
- yellow antimony (non-metallic)
- black antimony (non-metallic)
- (a fourth one too)
Polonium has two metallic allotropes. Antimony (IPA (Received Pronunciation, /ˈæntɪmoʊni/ (US is a Chemical element with the symbol Sb (stibium meaning "mark" and Polonium (pəˈloʊniəm is a Chemical element with the symbol Po and Atomic number 84 discovered in 1898 by Marie and Pierre Curie
Metals
- grey tin (alpha-tin)
- white tin (beta tin)
- rhombic tin (gamma)
- ferrite (alpha iron) - forms below 770°C (the Curie point, Tc ); the iron becomes magnetic in its alpha form; BCC
- beta - forms below 912°C (BCC)
- gamma - forms below 1401°C; face centred cubic (FCC) crystal structure
- delta - forms from cooling down molten iron below 1535°C; has a body-centred cubic (BCC) crystal structure
Titanium has two allotropes
Strontium has three allotropes
Lantanides and actinides
- Plutonium has six distinct solid allotropes under "normal" pressures. Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 See also Iron Iron represents perhaps the best-known example for Allotropy in a metal Ferrite or alpha iron ( α-Fe) is a Materials science term for Iron, or a Solid solution with iron as the main constituent with a Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Strontium (ˈstrɒntiəm /ˈstrɒnʃiəm/) is a Chemical element with the symbol Sr and the Atomic number 38 See also Plutonium, Allotrope Even at ambient pressure plutonium occurs in a variety of Allotropes These allotropes differ widely in crystal structure Their densities vary within a ratio of some 4:3, which vastly complicates all kinds of work with the metal (particularly casting, machining, and storage). A seventh plutonium allotrope exists at very high pressures, which adds further difficulties in exotic applications.
- Ytterbium has three allotropes
- Terbium has two crystalline allotropes
- Promethium has two allotropic forms
- Curium has 3 allotropes (also Americium, Berkelium, Californium do) [3]
References
- ^ Allotrope in IUPAC Compendium of Chemical Terminology, Electronic version, http://goldbook.iupac.org/A00243.html. Accessed March 2007.
- ^ Jensen W. B. , "The Origin of the Term Allotrope", Journal of Chemical Education, 2006, 83, 838-9
- ^ http://www.iop.org/EJ/article/0305-4608/15/2/002/jfv15i2pL29.pdf?request-id=AFlRqDDL3BGhbarg2wi7Kg
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