white metal: see Babbitt metal.

type metal, alloy of lead with antimony, tin, and sometimes copper, so named because of its one time extensive use for making printing type. Expanding upon solidification, the alloy takes a fine and clear impression of the mold in which it hardens. It has a low melting point. Once used extensively for type, it is also employed in making the metal parts of various musical instruments and for ornaments of intricate design and pattern. The percentages of the metals in the alloy vary, according to the use to which it is to be put.

metal, chemical element 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 ion, and the ability to conduct heat and electricity. The metals comprise about two thirds of the known elements (see periodic table). 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 nonmetals 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 series, 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 table determined by similar arrangements of their orbital electrons and a consequent similarity in chemical properties. Groups of similar metals include the alkali metals (Group 1 in the periodic table), the alkaline-earth metals (Group 2 in the periodic table), and the rare-earth metals (the lanthanide and actinide series of Group 3). Most metals other than the alkali metals and the alkaline earth metals are called transition metals (see transition elements). The oxidation states, or valence, 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 ores. The separation of metals from their ores is called extractive metallurgy. Metals are mixed with each other in definite amounts to form alloys; a mixture of mercury and another metal is called an amalgam. Bronze is an alloy of copper and tin, and brass contains copper and zinc. Steel 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 reduction). Finely divided metals or their oxides are often used as surface catalysts. Iron and iron oxides catalyze the conversion of hydrogen and nitrogen to ammonia in the Haber process. Finely divided catalytic platinum or nickel is used in the hydrogenation of unsaturated oils. Metal ions orient electron-rich groups called ligands around themselves, forming complex ions. Metal ions are important in many biological functions, including enzyme and coenzyme action, nucleic acid synthesis, and transport across membranes.

For the uses of specific metals, see separate articles.

britannia metal, silvery-white alloy of tin with antimony, copper, and sometimes bismuth and zinc. It is very similar in appearance to pewter, but is harder. It is used widely for the manufacture of tableware.

bell metal: see bronze.

Dutch metal: see brass.

Babbitt metal, an antifriction metal first produced by Isaac Babbitt in 1839. In present-day usage the term is applied to a whole class of silver-white bearing metals, or "white metals." These alloys usually consist of relatively hard crystals embedded in a softer matrix, a structure important for machine bearings. They are composed primarily of tin, copper, and antimony, with traces of other metals added in some cases and lead substituted for tin in others.

Any chemical element with valence electrons in two shells instead of only one. This structure gives them their outstanding ability to form ions containing more than one atom (complex ions, or coordination compounds), with a central atom or ion (often of a transition metal) surrounded by ligands in a regular arrangement. Theories on the bonding in these ions are still being refined. The elements in the periodic table from scandium to copper (atomic numbers 21–29), yttrium to silver (39–47), and lanthanum to gold (57–79, including the lanthanide series) are frequently designated the three main transition series. (Those in the actinide series and beyond, 89–111, also qualify.) All are metals, many of major economic or industrial importance (e.g., iron, gold, nickel, titanium). Most are dense, hard, and brittle, conduct heat and electricity well, have high melting points, and form alloys with each other and other metals. Their electronic structure lets them form compounds at various valences. Many of these compounds are coloured and paramagnetic (see paramagnetism) and (as do the metals themselves) often act as catalysts. Seealso rare earth metal.

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Used metals that are an important source of industrial metals and alloys, particularly in the production of steel, copper, lead, aluminum, and zinc. Smaller amounts of tin, nickel, magnesium, and precious metals are also recovered from scrap. Impurities consisting of such organic materials as wood, plastic, paint, and fabric can be burned off. Scrap is usually blended and remelted to produce alloys similar to or more complex than those from which the scrap was derived. Seealso recycling.

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Any of a large class of chemical elements including scandium (atomic number 21), yttrium (39), and the 15 elements from 57 (lanthanum) to 71 (see lanthanides). The rare earths themselves are pure or mixed oxides of these metals, originally thought to be quite scarce; however, cerium, the most plentiful, is three times as abundant as lead in the Earth's crust. The metals never occur free, and the pure oxides never occur in minerals. These metals are similar chemically because their atomic structures are generally similar; all form compounds in which they have valence 3, including stable oxides, carbides, and borides.

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or silverpoint

Method of drawing with a small sharpened metal rod—of lead, copper, gold, or most commonly silver—on specially prepared paper or parchment. Silverpoint produces a fine gray line that oxidizes to a light brown; the technique is best suited for small-scale work. It first appeared in medieval Italy and achieved great popularity in the 15th century. Albrecht Dürer and Leonardo da Vinci were its greatest exponents. It went out of fashion in the 17th century with the rise of the graphite pencil but was revived in the 18th century by the miniaturists and in the 20th century by Joseph Stella.

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Weakened condition of metal parts of machines, vehicles, or structures caused by repeated stresses or loadings, ultimately resulting in fracture under a stress much weaker than that necessary to cause fracture in a single application. Fatigue-resistant metals have been developed and their performance improved by surface treatments, and fatigue stresses have been significantly reduced in aircraft and other applications by designing to avoid stress concentrations.

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Any of a class of substances with, to some degree, the following properties: good heat and electricity conduction, malleability, ductility, high light reflectivity, and capacity to form positive ions in solution and hydroxides rather than acids when their oxides meet water. About three-quarters of the elements are metals; these are usually fairly hard and strong crystalline (see crystal) solids with high chemical reactivity that readily form alloys with each other. Metallic properties increase from lighter to heavier elements in each vertical group of the periodic table and from right to left in each row. The most abundant metals are aluminum, iron, calcium, sodium, potassium, and magnesium. The vast majority are found as ores rather than free. The cohesiveness of metals in a crystalline structure is attributed to metallic bonding: The atoms are packed close together, with their very mobile outermost electrons all shared throughout the structure. Metals fall into the following classifications (not mutually exclusive and most not rigidly defined): alkali metals, alkaline earth metals, transition elements, noble (precious) metals, platinum metals, lanthanide (rare earth) metals, actinide metals, light metals, and heavy metals. Many have essential roles in nutrition or other biochemical functions, often in trace amounts, and many are toxic as both elements and compounds (see mercury poisoning, lead poisoning).

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Type of rock music marked by highly amplified, distorted “power chords” on electric guitar, a hard beat, thumping bass, and often dark lyrics. It evolved in Britain and the U.S. in the late 1960s from the heavy, blues-oriented music of Steppenwolf, Jimi Hendrix, and others. In the 1970s the genre was defined by the music of bands such as Led Zeppelin, Black Sabbath, Kiss, AC/DC, and Aerosmith. After a period of decline, a new generation of bands such as Def Leppard, Iron Maiden, Mötley Crüe, and Van Halen revived heavy metal in the 1980s, along with the careers of many of its pioneers, including Ozzy Osbourne of Black Sabbath.

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Any of the six chemical elements in the second leftmost group of the periodic table (beryllium, magnesium, calcium, strontium, barium, and radium). Their name harks back to medieval alchemy. Their atoms have two electrons in the outermost shell, so they react readily, form numerous compounds, and are never found free in nature.

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Any of the six chemical elements in the leftmost group of the periodic table (lithium, sodium, potassium, rubidium, cesium, and francium). They form alkalies when they combine with other elements. Because their atoms have only one electron in the outermost shell, they are very reactive chemically (they react rapidly, even violently, with water), form numerous compounds, and are never found free in nature.

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