Metal

:''For alternative meanings see metal (disambiguation).'' In chemistry, a metal (Greek language: ''Metallon'') is an chemical element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals. Nonmetal elements are more abundant in nature than are metallic elements, but metals in fact constitute most of the periodic table. Some well-known metals are aluminium, copper, gold, iron, lead, silver, titanium, uranium, and zinc. The allotropes of metals tend to be lustrous, ductile, malleable, and good Conductor (material)s, while nonmetals generally speaking are brittle (for solid nonmetals), lack luster, and are insulators. A more modern definition of metals is that they have overlapping conductance and valence bands 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 of elemental metals. ==Physical properties== Traditionally, metals have certain characteristic physical properties: they are usually shiny (they have "lustre"), have a high density, are ductile and malleable, usually have a high melting point, are usually hard, and conduct electricity and heat well. However, this is mainly because the low density, soft, low melting point metals happen to be reactive and we rarely encounter them in their elemental, metallic form. The properties of conductivity are mainly because each atom exerts only a loose hold on its outermost electrons (valence electrons); thus, the valence electrons form a sort of sea around the close-packed metal nucleii cations. Most metals are chemically unstable, reacting with oxygen in the air to form oxides over varying timescales (iron rust over years, potassium burns in seconds, silver tarnish in months). The alkali metals react quickest followed by the alkaline earth metals, found in the leftmost two groups of the periodic table. The transition metals take much longer to oxidize (e.g. iron, copper, zinc, nickel), and palladium, platinum and gold do not react with atmospheric oxygen at all (which is why we make shiny jewelry from them). 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 (e.g. aluminium, some steels, titanium and more). Painting or anodizing metals are good ways to prevent their oxidation. ==Alloys== An alloy is a mixture with metallic properties that contains at least one metal element. 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 engines, may contain more than ten elements. ==Metal oxides== The oxides of metals are Base (chemistry); those of nonmetals are acidic. ==See also== * screening * metallic bond Metals Solid state physics Metallic elements Metalworking nds:Metall simple:Metal zh-cn:金属

Metal

I don't want to start an edit war, but some of the alkali metals can be cut with a knife, which means they are soft. The reason why usually high melting-points is necessary is mercury, rubidium, gallium, and cesium are all liquid at or near room temperature. While the concept of high MP or low MP differs, everyone on the planet would agree that these are low in comparison to the melting points of other metals (eg. tungsten). Mercury's melting point is below 0C. All people would agree that that is low. What metal oxides are basic? Most metal oxides are completely inert. Al2O3, SiO2, TiO, etc. Metal ''hydroxides'' are basic (NaOH, KOH), sure, but that's an entirely different animal. : User:Eaolson 22:34, 29 Jan 2005 (UTC)

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