Metal 19042 226172582 2008-07-17T04:01:03Z ClueBot 4928500 Reverting possible vandalism by [[Special:Contributions/24.111.182.219|24.111.182.219]] to version by Fieldday-sunday. False positive? [[User:ClueBot/FalsePositives|Report it]]. Thanks, [[User:ClueBot]]. (442191) (Bot) {{Refimprove|date=August 2007}} {{Mergefrom|Properties and uses of metals|date=June 2007}} {{Otheruses1|metallic materials}} [[Image:Hot metalwork.jpg|thumb|250px|Hot metal work from a [[blacksmith]].]] In chemistry, a '''metal''' ([[Greek language|Greek]]: ''Metallon'') is defined as an [[chemical element|element]] that readily loses electrons to form positive [[ion]]s ([[cations]]) and forms [[metallic bond]]s between other metal atoms<ref name="morty">Mortimer, Charles E. <u>Chemistry: A Conceptual Approach.</u> 3rd ed. New York: D. Van Nostrad Company, 1975.</ref> (forming [[ionic bonds]] with non-metals). == Definition == The metals of the periodic table are formally defined as [[Lithium]], [[beryllium]], [[sodium]], [[magnesium]], [[aluminium]], [[potassium]], [[calcium]], [[scandium]], [[titanium]], [[vanadium]], [[chromium]], [[manganese]], [[iron]], [[cobalt]], [[nickel]], [[copper]], [[zinc]], [[gallium]], [[rubidium]], [[strontium]], [[yttrium]], [[zirconium]], [[niobium]], [[molybdenum]], [[technetium]], [[ruthenium]], [[rhodium]], [[palladium]], [[silver]], [[cadmium]], [[indium]], [[tin]], [[antimony]], [[caesium]], [[barium]], [[lanthanum]], [[hafnium]], [[tantalum]], [[tungsten]], [[rhenium]], [[osmium]], [[iridium]], [[platinum]], [[gold]], [[mercury (element)|mercury]], [[thallium]], [[lead]], and [[bismuth]].<ref name="morty"/> Metals are sometimes described as a [[Crystal structure|lattice]] of positive ions surrounded by a cloud of delocalized [[electron]]s. are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the [[metalloid]]s and [[nonmetal]]s. On the [[Periodic table (metals and non-metals)|periodic table]], a diagonal line drawn from [[boron]] (B) to [[polonium]] (Po) separates the metals from the nonmetals. Most elements on this line are metalloids, sometimes called [[Semimetal|semi-metals]]; elements to the lower left are metals; elements to the upper right are nonmetals (see the [[Periodic table (metals and non-metals)|periodic table showing the metals]]). {{TOCleft}} An alternative definition of metals is that they have overlapping [[conduction band]]s and [[valence band]]s in their electronic structure. This definition opens up the category for metallic polymers and other organic metals, which have been made by researchers and employed in high-tech devices. These synthetic materials often have the characteristic silvery-grey reflectiveness (luster) of elemental metals. ==Chemical properties== Metals are usually inclined to form [[cations]] through electron loss,<ref name="morty"/> reacting with oxygen in the air to form [[oxide]]s over changing timescales (iron [[rust]]s over years, while [[potassium]] burns in seconds). The [[alkali metal]]s are the most [[volatility|volatile]], followed by the [[alkaline earth metal]]s, found in the leftmost two groups of the [[periodic table]]. Examples: :4Na + O<sub>2</sub> &rarr; 2Na<sub>2</sub>O (sodium oxide) :2Ca + O<sub>2</sub> &rarr; 2CaO (calcium oxide) :4Al + 3O<sub>2</sub> &rarr; 2Al<sub>2</sub>O<sub>3</sub> (aluminium oxide) The [[transition metal]]s (such as [[iron]], [[copper]], [[zinc]], and [[nickel]]) take much longer to oxidize. Others, like [[palladium]], [[platinum]] and [[gold]], do not react with the atmosphere at all. Some metals form a barrier layer of [[oxide]] on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades (like [[aluminium]], some [[steel]]s, and [[titanium]]). The [[oxide]]s of metals are [[Base (chemistry)|basic]] (as opposed to those of nonmetals, which are [[acid]]ic), although this may be considered a rule of thumb, rather than a fact. [[Painting]], [[anodising]] or [[plating]] metals are good ways to prevent their [[corrosion]]. However, a more reactive metal in the [[electrochemical series]] must be chosen for coating, especially when chipping of the coating is expected. Water and the two metals form an [[electrochemical cell]], and if the coating is less reactive than the coatee, the coating actually ''promotes'' corrosion. == Physical properties == [[Image:Gallium1 640x480.jpg|thumb|right|[[Gallium]] crystals]] Metals in general have superior [[electric conductivity|electric]] and [[thermal conductivity]], high [[lustre (mineralogy)|luster]] and [[density]], and the ability to be deformed under stress without [[cleavage|cleaving]].<ref name="morty"/> While there are several metals that have low density, hardness, and melting points, these (the [[alkali metals|alkali]] and [[alkaline earth]] metals) are extremely reactive, and are rarely encountered in their elemental, metallic form<ref name="morty"/>.<!-- The preceding paragraph from "metals in general" to "metallic form" is under the ref "Morty"; individual references for each part aren't needed 4/30/08 --> === Density === The majority of metals have higher densities than the majority of nonmetals<ref name="morty"/>. Nonetheless, there is wide variation in the densities of metals; [[lithium]] is the least dense solid element and [[osmium]] is the densest. The metals of groups [[I A]] and [[II A]] are referred to as the [[light metals]] because they are exceptions to this generalization<ref name="morty"/>. The high density of most metals is due to the tightly-packed crystal lattice of the metallic structure. The strength of metallic bonds for different metals reaches a maximum around the center of the transition series, as those elements have large amounts of delocalized electrons in a metallic bond. However, other factors (such as [[atomic radius]], [[nuclear charge]], number of bonding [[orbitals]], overlap of [[orbital energies]], and [[crystal form]]) are involved as well.<ref name="morty"/> === Malleability === The nondirectional nature of metallic bonding is thought to be the primary reason for the malleability of metal. Planes of atoms in a metal are able to slide across one another under stress, accounting for the ability of a crystal to deform without shattering. When the planes of an [[ionic bond]] are slid past one another, the resultant change in location shifts ions of the same charge into close proximity, resulting in the [[cleavage]] of the crystal. [[Covalent bond|Covalently bonded]] crystals can only be deformed by breaking the bonds between atoms, thereby resulting in [[fragmentation]] of the crystal. === Conductivity === The electrical and thermal conductivity of metals originate from the fact that in the [[metallic bond]], the outer electrons of the metal [[atoms]] form a gas of nearly free electrons, moving as an electron gas in a background of positive charge formed by the [[ion core]]s. Good mathematical predictions for electrical conductivity, as well as the electrons' contribution to the heat capacity and heat conductivity of metals can be calculated from the [[free electron model]], which does not take the detailed structure of the ion lattice into account. === Electric charge === When considering the exact band structure and binding energy of a metal, it is necessary to take into account the positive potential caused by the specific arrangement of the ion cores - which is periodic in [[crystal]]s. The most important consequence of the periodic potential is the formation of a small [[band gap]] at the boundary of the [[brillouin zone]]. Mathematically, the potential of the ion cores is treated in the [[nearly-free electron model]]. == Alloys == {{Main|Alloy}} An alloy is a mixture of two or more [[chemical element|elements]] in [[solid solution]] in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Examples of alloys are [[steel]] ([[iron]] and [[carbon]]), [[brass]] ([[copper]] and [[zinc]]), [[bronze]] ([[copper]] and [[tin]]), and [[duralumin]] ([[aluminium]] and [[copper]]). Alloys specially designed for highly demanding applications, such as [[jet engine]]s, may contain more than ten elements. == Categories == === Base metal === {{main|Base metal}} In [[chemistry]], the term ''''''base metal'''''' is used informally to refer to a metal that [[oxidation|oxidizes]] or [[corrosion|corrodes]] relatively easily, and reacts variably with dilute [[hydrochloric acid]] (HCl) to form [[hydrogen]]. Examples include [[iron]], [[nickel]], [[lead]] and [[zinc]]. [[Copper]] is considered a base metal as it oxidizes relatively easily, although it does not react with HCl. It is commonly used in opposition to [[noble metal]]. In [[alchemy]], a '''base metal''' was a common and inexpensive metal, as opposed to [[precious metal]]s, mainly [[gold]] and [[silver]]. A longtime goal of the alchemists was the transmutation of base metals into precious metals. In [[numismatics]], coins used to derive their value primarily from the [[precious metal]] content. Most modern currencies are [[fiat currency]], allowing the coins to be made of '''base metal'''. === Ferrous metal === {{main|Ferrous and non-ferrous metals}} The term "ferrous" is derived from the [[Latin language|latin word]] meaning "containing iron". This can include pure iron, such as [[wrought iron]], or an alloy such as [[steel]]. Ferrous metals are often [[magnetism|magnetic]], but not exclusively. === Noble metal === {{main|Noble metal}} '''Noble metals''' are metals that are resistant to [[corrosion]] or [[oxidation]], unlike most [[base metal]]s. They tend to be precious metals, often due to perceived rarity. Examples include [[tantalum]], [[gold]], [[platinum]], and [[rhodium]]. === Precious metal === {{main|Precious metal}} [[Image:GoldNuggetUSGOV.jpg|thumb|left|A [[gold]] nugget]] A '''precious metal''' is a rare metallic [[chemical element]] of high [[economic]] value. Chemically, the precious metals are less [[reactivity|reactive]] than most elements, have high [[Lustre (mineralogy)|luster]] and high electrical conductivity. Historically, precious metals were important as [[currency]], but are now regarded mainly as investment and industrial [[commodity|commodities]]. [[Gold]], [[silver]], [[platinum]] and [[palladium]] each have an [[ISO 4217]] currency code. The best-known precious metals are gold and silver. While both have industrial uses, they are better known for their uses in [[art]], [[jewelry]], and [[currency|coinage]]. Other precious metals include the [[platinum group]] metals: [[ruthenium]], [[rhodium]], [[palladium]], [[osmium]], [[iridium]], and [[platinum]], of which platinum is the most widely traded. [[Plutonium]] and [[uranium]] could also be considered precious metals. The demand for precious metals is driven not only by their practical use, but also by their role as investments and a [[store of value]]. Palladium was, as of summer 2006, valued at a little under half the price of gold, and platinum at around twice that of gold. Silver is substantially less expensive than these metals, but is often traditionally considered a precious metal for its role in coinage and jewelry. == Extraction == {{main|Ore|Mining}} Metals are often extracted from the Earth by means of mining, resulting in ores that are relatively rich sources of the requisite elements. Ore is located by [[prospecting]] techniques, followed by the exploration and examination of deposits. Mineral sources are generally divided into [[Surface mining|surface mines]], which are mined by excavation using heavy equipment, and [[sub-surface mining|subsurface mines]]. Once the ore is mined, the metals must be [[Extractive metallurgy|extracted]], usually by chemical or electrolytic reduction. [[Pyrometallurgy]] uses high temperatures to convert ore into raw metals, while [[hydrometallurgy]] employs [[aqueous]] chemistry for the same purpose. The methods used depend on the metal and their contaminants. {{Expand-section|date=June 2008}} == Metallurgy == {{main|Metallurgy}} Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. == Applications == Some metals and metal alloys possess high structural strength per unit mass, making them useful materials for carrying large loads or resisting impact damage. Metal alloys can be engineered to have high resistance to shear, torque and deformation. However the same metal can also be vulnerable to fatigue damage through repeated use, or from sudden stress failure when a load capacity is exceeded. The strength and resilience of metals has led to their frequent use in high-rise building and bridge construction, as well as most vehicles, many appliances, tools, pipes, non-illuminated signs and railroad tracks. The two most commonly used structural metals, [[iron]] and [[aluminium]], are also the most abundant metals in the [[Crust (geology)#Earth's crust|Earth's crust]].<ref>Frank Kreith and Yogi Goswami, eds. (2004). ''The CRC Handbook of Mechanical Engineering, 2nd edition.'' [[CRC]]: Boca Raton. p. 12-2. </ref> Metals are good conductors, making them valuable in electrical appliances and for carrying an electric current over a distance with little energy lost. Electrical power grids rely on metal cables to distribute electricity. Home electrical systems, for the most part, are wired with copper wire for its good conducting properties. The thermal conductivity of metal is useful for containers to heat materials over a flame. Metal is also used for [[heat sink]]s to protect sensitive equipment from overheating. The high reflectivity of some metals is important in the construction of mirrors, including precision astronomical instruments. This last property can also make metallic jewelry aesthetically appealing. Some metals have specialized uses; Radioactive metals such as [[Uranium]] and [[Plutonium]] are used in [[Nuclear reactor technology|nuclear power plants]] to produce energy via [[nuclear fission]]. Mercury is a liquid at room temperature and is used in switches to complete a circuit when it flows over the switch contacts. [[Shape memory alloy]] is used for applications such as pipes, fasteners and vascular [[stent]]s. However they are very good at conducting electricity and heat. == Trade == [[Image:2005metal import.PNG|thumb|right|Metal and [[ore]] imports in 2005]] The [[World Bank]] reports that China was the top importer of [[ores]] and metals in 2005 followed by the U.S.A. and Japan. == Astronomy == {{main|Metallicity}} In the specialised usage of [[astronomy]] and [[astrophysics]], the term "metal" is often used to refer to any element other than [[hydrogen]] or [[helium]], including substances as chemically non-metallic as [[neon]], [[fluorine]], and [[oxygen]]. Nearly all the hydrogen and helium in the [[Universe]] was created in [[Big Bang nucleosynthesis]], whereas all the "metals" were produced by [[nucleosynthesis]] in [[stars]] or [[supernova nucleosynthesis|supernovae]]. The [[Sun]] and the [[Milky Way Galaxy]] are composed of roughly 70% hydrogen, 30% helium, and 2% "metals" by mass.<ref>{{citation | last1=Sparke | first1=Linda S. | last2=Gallagher | first2=John S. | author2-link=John Gallagher III | title=Galaxies in the Universe | year=2000 | edition=1 | publisher=Cambridge University Press | ISBN=0521592410 | pages=8 }}</ref> ==See also== {{wiktionary}} <div style="-moz-column-count:3; column-count:3;"> *[[ASM International (society)]] *[[Amorphous metal]] *[[Electric field screening]] *[[Metalworking]] *[[Metallic bond]] *[[Metallurgy]] *[[Periodic table (metals and non-metals)]] *[[Properties and uses of metals]] *[[Steel]] *[[Structural steel]] *[[Transition metal]] </div> <categorytree> metallic elements </categorytree> == References == {{reflist}} ==External links== * [http://www.martindalecenter.com/GradMaterial_4_MA.html Martindale's "virtual" materials science center -- metals and alloys] {{PeriodicTablesFooter}} {{compact periodic table}} [[Category:Condensed matter physics]] [[Category:Metallic elements|*]] [[Category:Metals|*]] [[Category:Metalworking]] [[Category:Numismatics]] [[af:Metaal]] [[ar:فلز]] [[be:Метал]] [[bs:Metal (hemija)]] [[br:Metal]] [[bg:Метал]] [[ca:Metall]] [[cs:Kov]] [[cy:Metel]] [[da:Metal]] [[de:Metalle]] [[et:Metallid]] [[el:Μέταλλα]] [[es:Metal]] [[eo:Metalo (fiziko)]] [[fa:فلز]] [[fr:Métal]] [[gd:Meatailt]] [[hak:Kîm-su̍k]] [[ko:금속]] [[hi:धातु]] [[hr:Kovine]] [[id:Logam]] [[ia:Metallo]] [[is:Málmur]] [[it:Metallo]] [[he:מתכת]] [[jv:Logam]] [[ku:Lajwerd]] [[la:Metallum]] [[lv:Metāls]] [[lb:Metall]] [[lt:Metalai]] [[jbo:jinme]] [[lmo:Metai]] [[hu:Fémek]] [[mk:Метал]] [[ml:ലോഹം]] [[ms:Logam]] [[mn:Металл]] [[nl:Metaal]] [[ja:金属]] [[no:Metall]] [[nn:Metall]] [[nrm:Méta]] [[ug:مېتلا]] [[nds:Metall]] [[pl:Metale]] [[pt:Metal]] [[ro:Metal]] [[qu:Q'illay]] [[ru:Металлы]] [[simple:Metal]] [[sk:Kov]] [[sl:Kovina]] [[sr:Метал (хемија)]] [[sh:Metal (hemija)]] [[fi:Metalli]] [[sv:Metall]] [[tl:Metal]] [[ta:உலோகம்]] [[th:โลหะ]] [[vi:Kim loại]] [[chr:ᎠᎾᎦᎵᏍᎩ ᎦᏂᏱᏍᎩ]] [[tr:Metal (kimya)]] [[uk:Метали]] [[yi:מעטאל]] [[zh-yue:金屬]] [[zh:金属]]