nonmetal
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non·met·al
(nŏn-mĕt'l) 
n.
Any of a number of elements, such as oxygen or sulfur, that lack the physical and chemical properties of metals.
n.
Any of a number of elements, such as oxygen or sulfur, that lack the physical and chemical properties of metals.
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nonmetal
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The elements are conveniently, but arbitrarily, divided into metals and nonmetals. The nonmetals do not conduct electricity readily, are not ductile, do not have a complex refractive index, and in general have high ionization potentials.
If the periodic table is divided diagonally from upper left to lower right, all the nonmetals are on the right-hand side of the diagonal. Examples of elements which do not fit neatly into this useful but arbitrary classification are tin, which exists in two allotropic modifications, one definitely metallic and the other with many properties of a nonmetal, and tellurium and antimony. Such elements are called metalloids. See also Metalloid; Periodic table.
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Nonmetal
nonmetal, chemical element possessing certain properties by which it is distinguished from a metal. In general, this distinction is drawn on the basis that a nonmetal tends to accept electrons and form negative ions and that its oxide is acidic. Nonmetals are poor conductors of heat and electricity (see conduction) and do not have the luster of metals. Arsenic, antimony, selenium, and tellurium exhibit both nonmetallic and metallic properties and are called metalloids. Unlike the metals, which are all solids (with the exception of mercury) under ordinary conditions of temperature and pressure, the nonmetals appear in all three states. Argon, chlorine, fluorine, helium, hydrogen, krypton, neon, nitrogen, oxygen, and xenon are normally gases. Bromine is a liquid. Boron, carbon, iodine, phosphorus, silicon, and sulfur are solids. Certain of them, e.g., boron, carbon, iodine, silicon, and sulfur, form crystals, as do the metals. In hardness they vary considerably. Carbon in its allotropic form, the diamond, is the hardest element known. With the exception of carbon, sulfur, nitrogen, oxygen, and the inert gases-argon, helium, krypton, neon, and xenon-the nonmetals do not occur uncombined in nature, but exist in numerous relatively abundant compounds, among which are the oxides, halides (binary halogen compounds), sulfides, carbonates, nitrates, phosphates, silicates, and sulfates. With a few exceptions, the nonmetallic elements are important chiefly for their compounds. For the properties and uses of specific nonmetals, see the separate articles on these elements.
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categories related to 'nonmetal'
- Substances, Particles, and Atomic Architecture - nonmetal: any of a class of elements that typically gain electrons in chemical reactions, conduct heat and electricity poorly, and form anions or covalent bonds in compounds
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Nonmetal
Nonmetal, or non-metal, 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 periodic table can be termed either a metal or a nonmetal. (A few elements with intermediate properties are referred to as metalloids).
The elements generally regarded as nonmetals are:
- hydrogen
- In Group 14: carbon (C)
- In Group 15 (the pnictogens): nitrogen (N), phosphorus (P)
- In Group 16 (the chalcogens): oxygen (O), sulfur (S), selenium (Se)
- All elements (with the possible exception of ununseptium) in Group 17 - the halogens
- All elements (with the possible exception of ununoctium) in Group 18 - the noble gases
There is no rigorous definition for the term "nonmetal" - it covers a general spectrum of behaviour. Common properties considered characteristic of a nonmetal include:
- poor conductors of heat and electricity when compared to metals
- they form acidic oxides (whereas metals generally form basic oxides)
- in solid form, they are dull and brittle, rather than metals which are lustrous, ductile or malleable
- usually have lower densities than metals
- they have significantly lower melting points and boiling points than metals (with the exception of carbon)
- non-metals have high electronegativity
Only eighteen elements in the periodic table are generally considered nonmetals, compared to over eighty metals, but nonmetals make up most of the crust, atmosphere and oceans of the earth. Bulk tissues of living organisms are composed almost entirely of nonmetals. Most nonmetals are monatomic noble gases or form diatomic molecules in their elemental state, unlike metals which (in their elemental state) do not form molecules at all.
Metallic allotropes
Among the nonmetals, many possess metallic allotropes under high pressure, while some metals may exist in nonmetallic allotropes:
| Element | Period | Group | Classification | Allotropes |
|---|---|---|---|---|
| Hydrogen | 1 | 1 | nonmetal | Metallic hydrogen forms at 260-270 GPa at 295 K and converts back to molecular hydrogen at 200 GPa.[1] |
| Helium | 1 | 18 | noble gas | Metallic helium is predicted to occur around 100 Mbar (10 TPa) at low temperatures and 40 Mbar (4 TPa) at high temperatures.[2] |
| Boron | 2 | 13 | metalloid | Common allotropes of boron have bandgaps of approximately 2 eV, but a high-pressure superconducting phase occurs at 160 GPa and 250 GPa at 4 and 11 K.[3][4] |
| Carbon | 2 | 14 | nonmetal | A metallic allotrope of carbon has been hypothesized to occur at 1.1 THz.[5][6][7] |
| Nitrogen | 2 | 15 | nonmetal | There has been some theoretical consideration of a high-pressure metallic allotrope.[8] Despite a calculated transition at 100 GPa, experiments up to 180 GPa failed to detect this.[5] |
| Oxygen | 2 | 16 | nonmetal | Metallic oxygen has been observed at pressures over 96 GPa, and is superconducting at low temperatures.[9][10][11][12] |
| Fluorine | 2 | 17 | halogen | The metallization pressure of solid fluorine is expected to exceed 200 GPa.[13] |
| Neon | 2 | 18 | noble gas | First-principle calculations estimate that the band gap of neon might close at 142 TPa and metallization may occur at 176 TPa.[14] |
| Aluminium | 3 | 13 | poor metal | The structure of clusters of aluminium atoms sandwiched among other elements can be extended to hypothesize a nonmetallic "β-aluminium" allotrope; it is not known whether it can physically exist.[15] |
| Silicon | 3 | 14 | metalloid | Under increasing pressure silicon transforms from a cubic diamond structure to a β-tin (11-12 GPa), primitive hexagonal (13-16 GPa), hexagonal-close-packed (37-40 GPa), and face-centered cubic phases (78 GPa). Three of these phases are metallic.[16][17] |
| Phosphorus | 3 | 15 | nonmetal | Two allotropes of phosphorus at atmospheric pressure have sometimes been called metallic - "α-metallic" (violet or Hittorf's phosphorus) and "β-metallic" or black phosphorus. Violet and black phosphorus have bandgaps of 1.5 and 0.34 eV, respectively.[18][19] Black phosphorus metallizes at 1.7 GPa by bandgap closure without a structural transition.[5] |
| Sulfur | 3 | 16 | nonmetal | Sulfur undergoes transitions to two superconducting metal phases, at roughly 90 GPa and 200 GPa; the first of these has an incommensurate crystal structure.[20] |
| Chlorine | 3 | 17 | halogen | Chlorine was estimated to undergo transition to a metal at 67 GPa; this was confirmed, but at higher pressures.[5] |
| Argon | 3 | 18 | noble gas | As of 2009, metallization of argon, predicted to occur at very high pressures, has not been observed.[21] |
| Gallium | 4 | 13 | poor metal | The orthorhombic α-phase of gallium includes a short covalent bond between two of eight atoms of the unit cell, and has a "deep minimum in the electronic density of states at the Fermi energy"; thus it can be called a "metallic molecular crystal" or an "inorganic polymer". These properties are absent in the metallic Ga-II and β-Ga states.[22] |
| Germanium | 4 | 14 | metalloid | Germanium undergoes a semiconductor to metal transition at 11 GPa.[5] |
| Arsenic | 4 | 15 | metalloid | |
| Selenium | 4 | 16 | nonmetal | Selenium undergoes a semiconductor to metal transition at 20 GPa.[5] |
| Bromine | 4 | 17 | halogen | Bromine undergoes a semiconductor to metal transition at 100 GPa.[5] |
| Krypton | 4 | 18 | noble gas | Metallization of krypton was predicted to occur at 316 GPa.[23] |
| Indium | 5 | 13 | poor metal | |
| Tin | 5 | 14 | poor metal | Of the two common allotropes of tin at room temperature and pressure, white tin (β-tin) is metallic, but gray tin (α-tin) is not. Gray tin is more stable at colder temperatures. |
| Antimony | 5 | 15 | metalloid | |
| Tellurium | 5 | 16 | metalloid | Tellurium undergoes a semiconductor to metal transition at 4 GPa.[5] |
| Iodine | 5 | 17 | halogen | Iodine undergoes a semiconductor to metal transition at 17 GPa.[5] |
| Xenon | 5 | 18 | noble gas | Xenon undergoes a semiconductor to metal transition at 160 GPa.[5] |
| Thallium | 6 | 13 | poor metal | |
| Lead | 6 | 14 | poor metal | |
| Bismuth | 6 | 15 | poor metal | |
| Polonium | 6 | 16 | metalloid | |
| Astatine | 6 | 17 | halogen | |
| Radon | 6 | 18 | noble gas |
See also
- ^ Eremets, M.I.; Troyan, I.A. (2011). "Conductive dense hydrogen". Nature Materials 10 (12). Bibcode 2011NatMa..10..927E. doi:10.1038/nmat3175. http://www.nature.com/nmat/journal/v10/n12/full/nmat3175.html.
- ^ David J. Stevenson (2008-08-06). Metallic helium in massive planets. PNAS. http://www.pnas.org/content/105/32/11035.full.
- ^ M. I. Eremets et al. (2001). "Superconductivity in Boron". Science 293 (5528): 272–4. Bibcode 2001Sci...293..272E. doi:10.1126/science.1062286. PMID 11452118.
- ^ C. Mailhiot, J. B. Grant, and A. K. McMahan (1990). "High-pressure metallic phases of boron". Phys. Rev. B 42 (14): 9033. Bibcode 1990PhRvB..42.9033M. doi:10.1103/PhysRevB.42.9033.
- ^ a b c d e f g h i j By Tadeusz Suski, William Paul. High pressure in semiconductor physics, Volume 55. http://books.google.com/books?id=FdOVTEW9vE0C&pg=PA425&lpg=PA425&ots=JmIfeSiu9l&dq=phosphorus+TPa+%22high+pressure%22.
- ^ Roald Hoffmann, Timothy Hughbanks, Miklos Kertesz, Peter H. Bird (1983-07). "Hypothetical metallic allotrope of carbon". J. Am. Chem. Soc. 105 (14): 4831–4832. doi:10.1021/ja00352a049. http://pubs.acs.org/doi/abs/10.1021/ja00352a049.
- ^ Correa, Aa; Bonev, Sa; Galli, G (Jan 2006). "Carbon under extreme conditions: phase boundaries and electronic properties from first-principles theory". Proceedings of the National Academy of Sciences of the United States of America 103 (5): 1204–8. Bibcode 2006PNAS..103.1204C. doi:10.1073/pnas.0510489103. ISSN 0027-8424. PMC 1345714. PMID 16432191. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=16432191.
- ^ "Abstract: B30.00012 : Metallic nitrogen at high pressure and temperature". American Physical Society. http://meetings.aps.org/Meeting/MAR10/Event/117241.
- ^ Akahama, Yuichi; Haruki Kawamura, Daniel Häusermann, Michael Hanfland, and Osamu Shimomura (June 1995). "New High-Pressure Structural Transition of Oxygen at 96 GPa Associated with Metallization in a Molecular Solid". Physical Review Letters 74 (23): 4690–4694. Bibcode 1995PhRvL..74.4690A. doi:10.1103/PhysRevLett.74.4690. PMID 10058574.
- ^ Peter P. Edwards, Friedrich Hensel (2002). "Metallic Oxygen". ChemPhysChem (Weinheim, Germany: WILEY-VCH-Verlag) 3 (1): 53–56. doi:10.1002/1439-7641(20020118)3:1<53::AID-CPHC53>3.0.CO;2-2. PMID 12465476.
- ^ Desgreniers, S., Vohra, Y. K. & Ruoff, A. L. (1990). "Optical response of very high density solid oxygen to 132 GPa". J. Phys. Chem. 94 (3): 1117–1122. doi:10.1021/j100366a020.
- ^ Shimizu, K., Suhara, K., Ikumo, M., Eremets, M. I. & Amaya, K. (1998). "Superconductivity in oxygen". Nature 393 (6687): 767–769. Bibcode 1998Natur.393..767S. doi:10.1038/31656.
- ^ Kazunari Kususe, Yuzo Hori, Shugo Suzuki and Kenji Nakao (1999). "Theoretical Study of Geometries and Electronic Structures of Solid Oxygen under High Pressures". J. Phys. Soc. Jpn. 68: 2692–2696. Bibcode 1999JPSJ...68.2692K. doi:10.1143/JPSJ.68.2692. http://jpsj.ipap.jp/link?JPSJ/68/2692/.
- ^ Yi-guang Hea, Xiu-zhang Tanga, Yi-kang Pub (2010-10-15). "First-principle study of solid neon under high compression". Physica B: Condensed Matter 405 (20): 4335–4338. Bibcode 2010PhyB..405.4335H. doi:10.1016/j.physb.2010.07.037. http://www.sciencedirect.com/science/article/pii/S0921452610007362.
- ^ Hansgeorg Schnöckel (2010). "Structures and Properties of Metalloid Al and Ga Clusters Open Our Eyes to the Diversity and Complexity of Fundamental Chemical and Physical Processes during Formation and Dissolution of Metals". pp. 4125–4163. ftp://111.68.111.206/e-Journal/Chemical%20Reviews/Vol.%20110/No.%207/4125%964163.pdf.
- ^ M.Hanflund et al. (1988-12-15). "Optical properties of metallic silicon". Physical Review B 38 (11). http://users-phys.au.dk/nec/Papers/necPRB2/PRB3812864.pdf.
- ^ "New phases of semiconductors at ultrahigh pressure". pp. Supplement C8-407. http://hal.archives-ouvertes.fr/docs/00/22/43/76/PDF/ajp-jphyscol198445C874.pdf.
- ^ A. Holleman, N. Wiberg (1985). "XV 2.1.3". Lehrbuch der Anorganischen Chemie (33 ed.). de Gruyter. ISBN 3-11-012641-9.
- ^ Berger, L. I. (1996). Semiconductor materials. CRC Press. p. 84. ISBN 0-8493-8912-7. http://books.google.com/?id=Ty5Ymlg_Mh0C&pg=PA84.
- ^ "Incommensurate Metallic Sulfur above 100 GPa". ESRF. 2006-09-13. http://www.esrf.eu/UsersAndScience/Publications/Highlights/2005/Materials/MAT1.
- ^ Gabriel Joseph Hanna (1999). "Confocal microscopy of fluid argon under pressure". (Ph.D. dissertation for Washington State University). http://udini.proquest.com/view/confocal-microscopy-of-fluid-argon-pqid:2002828811/.
- ^ "Investigation of gallium as a nonlinear material". http://www.orc.soton.ac.uk/publications/theses/1390T_pp/1390T_Chap4.pdf.
- ^ Juichiro Hama, Kaichi Suito (1989-09-11). "Equation of state and metallization in compressed solid krypton". Physics Letters A 140 (3): 117–121. Bibcode 1989PhLA..140..117H. doi:10.1016/0375-9601(89)90503-3. http://www.sciencedirect.com/science/article/pii/0375960189905033.
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| H | He | |||||||||||||||||||||||||||||||||||||||||
| Li | Be | B | C | N | O | F | Ne | |||||||||||||||||||||||||||||||||||
| Na | Mg | Al | Si | P | S | Cl | Ar | |||||||||||||||||||||||||||||||||||
| K | Ca | Sc | Ti | V | Cr | Mn | Fe | Co | Ni | Cu | Zn | Ga | Ge | As | Se | Br | Kr | |||||||||||||||||||||||||
| Rb | Sr | Y | Zr | Nb | Mo | Tc | Ru | Rh | Pd | Ag | Cd | In | Sn | Sb | Te | I | Xe | |||||||||||||||||||||||||
| Cs | Ba | La | Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg | Tl | Pb | Bi | Po | At | Rn | |||||||||||
| Fr | Ra | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | Uuq | Uup | Uuh | Uus | Uuo | |||||||||||
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