Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nded.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. A metal (from Ancient Greek μέταλλον ( métallon)'mine, quarry, metal') is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically ductile (can be drawn into wires) and malleable (they can be hammered into thin sheets). These properties are the result of the metallic bond between the atoms or molecules of the metal. Miss Armit: Well, we've got copper and it's a really good conductor of electricity, so we use that in our wires. We've also got iron and aluminium and they're great at conducting heat, so we use these metals for our pots and pans. And gold and silver are used in jewellery, because they're shiny, they're malleable and unreactive with oxygen, so they don't rust easily. Tylecote, R. F. (1992). A History of Metallurgy, Second Edition. London: Maney Publishing, for the Institute of Materials. ISBN 978-1-902653-79-2. Archived from the original on 2015-04-02.

The role of metallic elements in the evolution of cell biochemistry has been reviewed, including a detailed section on the role of calcium in redox enzymes. [32] Metals are relatively good conductors of heat. The electrons in a metal's electron cloud are highly mobile and easily able to pass on heat-induced vibrational energy.Published in The Delineator, Sept. 1909. Reprinted as the introduction to Rewards and Fairies in 1910. Observations and equations for reaction of some metals in the reactive series with air, are shown in the table below. Metal Not all metals have these properties. Mercury, for instance, is liquid at room temperature, Lead, is very soft, and heat and electricity do not pass through iron as well as they do through copper. Heat and electricity can easily pass through a metal (it is conductive). A lump of metal can be beaten into a thin sheet (it is malleable) or can be pulled into thin wires (it is ductile). Metal is hard to pull apart (it has a high tensile strength) or smash (it has a high compressive strength). If you push on a long, thin piece of metal, it will bend, not break (it is elastic). Except for cesium, copper, and gold, metals have a neutral, silvery color. A metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as polymeric sulfur nitride. [1]

The Earth's crust is made of approximately 25% of metals by weight, of which 80% are light metals such as sodium, magnesium, and aluminium. Nonmetals (~75%) make up the rest of the crust. Despite the overall scarcity of some heavier metals such as copper, they can become concentrated in economically extractable quantities as a result of mountain building, erosion, or other geological processes. Tunay, Olcay; Kabdasli, Isik; Arslan-Alaton, Idil; Olmez-Hanci, Tugba (2010). Chemical Oxidation Applications for Industrial Wastewaters. IWA Publishing. ISBN 978-1-84339-307-8. Raymond R. 1984, Out of the fiery furnace: The impact of metals on the history of mankind, Macmillan Australia, Melbourne, ISBN 978-0-333-38024-6 In some cases, for example in the presence of high energy gamma rays or in a very high temperature hydrogen rich environment, the subject nuclei may experience neutron loss or proton gain resulting in the production of (comparatively rare) neutron deficient isotopes. [21] In astronomy, a metal is any element other than hydrogen or helium. This is because these two elements (and sometimes lithium) are the only ones that form outside stars. In the sky, a spectrometer can see the signs of metals and show the astronomer the metals in a star.

When a metal ore is an ionic compound of that metal and a non-metal, the ore must usually be smelted—heated with a reducing agent—to extract the pure metal. Many common metals, such as iron, are smelted using carbon as a reducing agent. Some metals, such as aluminum and sodium, have no commercially practical reducing agent, and are extracted using electrolysis instead. [26] [27] Other significant metallic alloys are those of aluminum, titanium, copper, and magnesium. Copper alloys have been known since prehistory— bronze gave the Bronze Age its name—and have many applications today, most importantly in electrical wiring. The alloys of the other three metals have been developed relatively recently; due to their chemical reactivity they need electrolytic extraction processes. The alloys of aluminum, titanium, and magnesium are valued for their high strength-to-weight ratios; magnesium can also provide electromagnetic shielding. [ citation needed] These materials are ideal for situations where high strength-to-weight ratio is more important than material cost, such as in aerospace and some automotive applications. In physics, a metal is generally regarded as any substance capable of conducting electricity at a temperature of absolute zero. [2] Many elements and compounds that are not normally classified as metals become metallic under high pressures. For example, the nonmetal iodine gradually becomes a metal at a pressure of between 40 and 170 thousand times atmospheric pressure. Equally, some materials regarded as metals can become nonmetals. Sodium, for example, becomes a nonmetal at pressure of just under two million times atmospheric pressure.

Metals are typically malleable and ductile, deforming under stress without cleaving. [6] The nondirectional nature of metallic bonding is thought to contribute significantly to the ductility of most metallic solids. In contrast, in an ionic compound like table salt, when the planes of an ionic bond slide past one another, the resultant change in location shifts ions of the same charge closer, resulting in the cleavage of the crystal. Such a shift is not observed in a covalently bonded crystal, such as a diamond, where fracture and crystal fragmentation occurs. [7] Reversible elastic deformation in metals can be described by Hooke's Law for restoring forces, where the stress is linearly proportional to the strain.

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. Most metals are solid at room temperature, but this does not have to be the case. Mercury is liquid. Alloys are mixtures, where at least one part of the mixture is a metal. Examples of metals are aluminium, copper, iron, tin, gold, lead, silver, titanium, uranium, and zinc. Well-known alloys include bronze and steel. The high reflectivity of some metals enables their use in mirrors, including precision astronomical instruments, and adds to the aesthetics of metallic jewelry. The gas collected in the boiling tube can be tested for hydrogen - a lighted wooden splint makes a popping sound in a boiling tube of hydrogen. See also: Abundance of the chemical elements A sample of diaspore, an aluminum oxide hydroxide mineral, α-AlO(OH)