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metal,

chemical elementelement,
in chemistry, a substance that cannot be decomposed into simpler substances by chemical means. A substance such as a compound can be decomposed into its constituent elements by means of a chemical reaction, but no further simplification can be achieved.
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 displaying certain properties by which it is normally distinguished from a nonmetal, notably its metallic luster, the capacity to lose electrons and form a positive ionion,
atom or group of atoms having a net electric charge. Positive and Negative Electric Charges

A neutral atom or group of atoms becomes an ion by gaining or losing one or more electrons or protons.
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, and the ability to conduct heat and electricity. The metals comprise about two thirds of the known elements (see periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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). Some metals, including copper, tin, iron, lead, gold, silver, and mercury, were known to the ancients; copper is probably the oldest known metal.

Physical Properties

Metals differ so widely in hardness, ductility (the potentiality of being drawn into wire), malleability, tensile strength, density, and melting point that a definite line of distinction between them and the nonmetalsnonmetal,
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.
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 cannot be drawn. The hardest elemental metal is chromium; the softest, cesium. Copper, gold, platinum, and silver are especially ductile. Most metals are malleable; gold, silver, copper, tin, and aluminum are extremely so. Some metals exhibiting great tensile strength are copper, iron, and platinum. Three metals (lithium, potassium, and sodium) have densities of less than one gram per cubic centimeter at ordinary temperatures and are therefore lighter than water. Some heavy metals, beginning with the most dense, are osmium, iridium, platinum, gold, tungsten, uranium, tantalum, mercury, hafnium, lead, and silver.

For many industrial uses, the melting points of the metals are important. Tungsten fuses, or melts, only at extremely high temperatures (3,370°C;.), while cesium has a melting point of 28.5°C;. The best metallic conductor of electricity is silver. Copper, gold, and aluminum follow in the order named. All metals are relatively good conductors of heat; silver, copper, and aluminum are especially conductive. The radioactive metal uranium is used in reactor piles to generate steam and electric power. Plutonium, another radioactive element, is used in nuclear weapons and nuclear reactors as well as in pacemakers. Some of the radioactive metals not found in nature, e.g., fermium and seaborgium, are produced by nuclear bombardment.

Some elements, e.g., arsenic and antimony, exhibit both metallic and nonmetallic properties and are called metalloids. Furthermore, although all metals form crystals, this is also characteristic of certain nonmetals, e.g., carbon and sulfur.

Chemical Properties

Chemically, the metals differ from the nonmetals in that they form positive ions and basic oxides and hydroxides. Upon exposure to moist air, a great many undergo corrosion, i.e., enter into a chemical reaction; e.g., iron rusts when exposed to moist air, the oxygen of the atmosphere uniting with the metal to form the oxide of the metal. Aluminum and zinc do not appear to be affected, but in fact a thin coating of the oxide is formed almost at once, stopping further action and appearing unnoticeable because of its close resemblance to the metal. Tin, lead, and copper react slowly under ordinary conditions. Silver is affected by compounds such as sulfur dioxide and becomes tarnished when exposed to air containing them. The metals are combined with nonmetals in their salts, as in carbides, carbonates, chlorides, nitrates, phosphates, silicates, sulfides, and sulfates.

The Electromotive Series

On the basis of their ability to be oxidized, i.e., lose electrons, metals can be arranged in a list called the electromotive serieselectromotive series,
list of metals whose order indicates the relative tendency to be oxidized, or to give up electrons (see oxidation and reduction); the list also includes the gas hydrogen. The electromotive series begins with the metal most easily oxidized, i.e.
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, or replacement series. Metals toward the beginning of the series, like cesium and lithium, are more readily oxidized than those toward the end, like silver and gold. In general, a metal will replace any other metal, or hydrogen, in a compound that it precedes in the series, and under ordinary circumstances it will be replaced by any metal, or hydrogen, that it follows.

Metals in the Periodic Table

Metals fall into groups in the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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 determined by similar arrangements of their orbital electronselectron,
elementary particle carrying a unit charge of negative electricity. Ordinary electric current is the flow of electrons through a wire conductor (see electricity). The electron is one of the basic constituents of matter.
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 and a consequent similarity in chemical properties. Groups of similar metals include the alkali metalsalkali metals,
metals found in Group 1 of the periodic table. Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univalent compounds.
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 (Group 1 in the periodic table), the alkaline-earth metalsalkaline-earth metals,
metals constituting Group 2 of the periodic table. Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducing agents, but they are exceeded in each of these properties by the
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 (Group 2 in the periodic table), and the rare-earth metalsrare-earth metals,
in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually considered a rare-earth metal.
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 (the lanthanidelanthanide series,
a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series.
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 and actinide seriesactinide series,
a series of radioactive metallic elements in Group 3 of the periodic table. Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series.
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 of Group 3). Most metals other than the alkali metals and the alkaline earth metals are called transition metals (see transition elementstransition elements
or transition metals,
in chemistry, group of elements characterized by the filling of an inner d electron orbital as atomic number increases.
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). The oxidation states, or valencevalence,
combining capacity of an atom expressed as the number of single bonds the atom can form or the number of electrons an element gives up or accepts when reacting to form a compound.
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, of the metal ions vary from +1 for the alkali metals to as much as +7 for some transition metals.

Sources and Uses

Although a few metals occur uncombined in nature, the great majority are found combined in their oresore,
metal-bearing mineral mass that can be profitably mined. Nearly all rock deposits contain some metallic minerals, but in many cases the concentration of metal is too low to justify mining the ore.
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. The separation of metals from their ores is called extractive metallurgymetallurgy
, science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals economically from low-grade ores, with obtaining and refining rare metals hitherto not used, and with the
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. Metals are mixed with each other in definite amounts to form alloysalloy
[O. Fr.,=combine], substance with metallic properties that consists of a metal fused with one or more metals or nonmetals. Alloys may be a homogeneous solid solution, a heterogeneous mixture of tiny crystals, a true chemical compound, or a mixture of these.
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; a mixture of mercury and another metal is called an amalgamamalgam
, alloy containing mercury. The alloy may be liquid or solid, depending on the proportion of mercury, although all naturally occurring amalgams, i.e., those of gold and silver, are solid. Amalgams are widely used.
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. Bronzebronze,
in metallurgy, alloy of copper, tin, zinc, phosphorus, and sometimes small amounts of other elements. Bronzes are harder than brasses. Most are produced by melting the copper and adding the desired amounts of tin, zinc, and other substances.
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 is an alloy of copper and tin, and brassbrass,
alloy having copper (55%–90%) and zinc (10%–45%) as its essential components. The properties of brass vary with the proportion of copper and zinc and with the addition of small amounts of other elements, such as aluminum, lead, tin, or nickel.
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 contains copper and zinc. Steelsteel,
alloy of iron, carbon, and small proportions of other elements. Iron contains impurities in the form of silicon, phosphorus, sulfur, and manganese; steelmaking involves the removal of these impurities, known as slag, and the addition of desirable alloying elements.
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 is an alloy of iron and other metals with carbon added for hardness.

Since metals form positive ions readily, i.e., they donate their orbital electrons, they are used in chemistry as reducing agents (see oxidation and reductionoxidation and reduction,
complementary chemical reactions characterized by the loss or gain, respectively, of one or more electrons by an atom or molecule. Originally the term oxidation
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). Finely divided metals or their oxides are often used as surface catalystscatalyst,
substance that can cause a change in the rate of a chemical reaction without itself being consumed in the reaction; the changing of the reaction rate by use of a catalyst is called catalysis.
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. Iron and iron oxides catalyze the conversion of hydrogen and nitrogen to ammonia in the Haber processHaber process
, commercial process for the synthesis of ammonia, NH3. Pure hydrogen and nitrogen gases are mixed in the appropriate proportion, heated to between 450°C; and 600°C;, compressed to about 1,000 atmospheres pressure, and passed over a catalyst.
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. Finely divided catalytic platinum or nickel is used in the hydrogenationhydrogenation
, chemical reaction of a substance with molecular hydrogen, usually in the presence of a catalyst. A common hydrogenation is the hardening of animal fats or vegetable oils to make them solid at room temperature and improve their stability.
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 of unsaturated oils. Metal ions orient electron-rich groups called ligandsligand
, charged or uncharged molecule with one or more unshared pairs of electrons that can attach to a central metallic atom or ion to form an aggregate known as a complex ion (see chemical bond). Some ligands that share electrons with metals form very stable complexes.
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 around themselves, forming complex ionscomplex ion,
charged molecular aggregate (see ion), consisting of a metallic atom or ion to which is attached one or more electron-donating molecules. In some complex ions, such as sulfate, SO4−2
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. Metal ions are important in many biological functions, including enzymeenzyme,
biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.
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 and coenzymecoenzyme
, any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes. A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in
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 action, nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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 synthesis, and transport across membranes.

For the uses of specific metals, see separate articles.

metal

In astronomy, any element heavier than helium; the most abundant metals are oxygen, carbon, and nitrogen.

Metal

Any of a class of elementary substances which are crystalline when solid and characterized by opacity, ductility and conductivity; mined in a form called “ore” and manufactured to specific applications.

aluminum

A lightweight metal which is malleable and nonmagnetic and has good conductivity; it is a good reflector of heat and light and is resistant to oxidation; it is often anodized for better corrosion resistance, color and surface hardness.

brass

Any copper alloy having zinc as the principal alloying element, but often with small quantities of other elements.

bronze

An alloy of copper and tin, bronze in color, having a substantial admixture of copper to modify the properties of the principal element, such as aluminum bronze and magnesium bronze.

cast iron

A hard, nonmalleable iron alloy containing carbon and silicon, which is poured into a sand mold and then machined to a desired architectural shape.

copper

A metal with good electrical conductivity, used for roofing, flashing, hardware and plumbing applications; when exposed to air, copper oxidizes and develops a greenish “patina” that halts corrosion.

ferrous metal

A metal in which iron is the principal element.

iron

A metallic element found in the earth’s crust, consisting of a malleable, ductile, magnetic substance from which pig iron and steel are manufactured.

lead

A soft, malleable, heavy metal that has a low melting point and a high coefficient of thermal expansion; very easy to cut and work.

stainless steel

A high-strength, tough steel alloy; contains chromium with nickel as an additional alloying element and is highly resistant to corrosion and rust.

steel

A hard and malleable metal when heated; produced by melting and refining it according to the carbon content; used for structural shapes due to its alloy of iron and carbon which has a malleable high tensile strength.

tin

A lustrous white, soft, and malleable metal having a low melting point; relatively unaffected by exposure to air; used for making alloys and solder, and in coating sheet metal.

weathering steel

A high-strength, low-alloy steel that forms an oxide coating when exposed to rain or moisture, which adheres to the base metal and protects it from further corrosion.

wrought iron

A commercially pure iron of fibrous nature, valued for its corrosion resistance and ductility; used for water pipes, water tank plates, rivets, and other forged work.

zinc

A hard bluish-white metal, brittle at normal temperatures, very malleable and ductile when heated; not subject to corrosion; used for galvanizing sheet steel and iron in various metal alloys.

What does it mean when you dream about metal?

Metals are hard but malleable, a potent symbol of strength and character. Metals can also be cold and, because of their association with technology, represent the inhuman side of our society.

metal

[′med·əl]
(astronomy)
In stellar spectroscopy, any element heavier than helium.
(materials)
An opaque crystalline material usually of high strength with good electrical and thermal conductivities, ductility, and reflectivity; properties are related to the structure, in which the positively charged ions are bonded through a field of free electrons which surrounds them forming a close-packed structure.

Metal

An electropositive chemical element. Physically, a metal atom in the ground state contains a partially filled band with an empty state close to an occupied state. Chemically, upon going into solution a metal atom releases an electron to become a positive ion. Consequently in biotic systems metal atoms function prominently in ionic transport and electron exchange. In bulk a metal has a high melting point and a correspondingly high boiling temperature; except for mercury, metals are solid at standard conditions. Direct observation shows a metal to be relatively dense, malleable, ductile, cohesive, highly conductive both electrically and thermally, and lustrous. When crystals of the elements are classified along a scale from plastic to brittle, metals fall toward the plastic end. Furthermore, molten metals mixed with each other over wide ranges of proportions form, upon slowly cooling, homogeneous close-packed crystals. In contrast, a metal mixed with a nonmetal completely combines into a homogeneous crystal only in one or a few discrete stoichiometric proportions.

metal

1. 
a. any of a number of chemical elements, such as iron or copper, that are often lustrous ductile solids, have basic oxides, form positive ions, and are good conductors of heat and electricity
b. an alloy, such as brass or steel, containing one or more of these elements
2. the substance of glass in a molten state or as the finished product
3. short for road metal
4. Astronomy any element heavier than helium
5. the rails of a railway

METAL

(1)
Mega-Extensive Telecommunications Applications Language. BBS language for PRODOS 8 on Apple II.

METAL

(2)
The syntax-definition formalism of the Mentor system. Metal specifications are compiled to specifications for a scanner/parser generator such as Lex/Yacc. "Metal: A Formalism to Specify Formalisms", G. Kahn et al, Sci Comp Prog 3:151-188 (1983).