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zirconium
Zirconium is a chemical element with symbol Zr and atomic number 40. The name of zirconium is taken from the name of the mineral zircon, the most important source of zirconium. The word ''zircon'' comes from the Persian word ''zargun'' زرگون, meaning "gold-colored". It is a lustrous, grey-white, strong transition metal that resembles hafnium and, to a lesser extent, titanium. Zirconium is mainly used as a refractory and opacifier, although it is used in small amounts as an alloying agent for its strong resistance to corrosion. Zirconium forms a variety of inorganic and organometallic compounds such as zirconium dioxide and zirconocene dichloride, respectively. Five isotopes occur naturally, three of which are stable. Zirconium compounds have no known biological role.
==Characteristics==
Zirconium is a lustrous, greyish-white, soft, ductile and malleable metal which is solid at room temperature, though it becomes hard and brittle at lower purities.〔〔 In powder form, zirconium is highly flammable, but the solid form is far less prone to ignition. Zirconium is highly resistant to corrosion by alkalis, acids, salt water and other agents.〔 However, it will dissolve in hydrochloric and sulfuric acid, especially when fluorine is present. Alloys with zinc become magnetic below 35 K.〔
Zirconium's melting point is 1855 °C (3371 °F), and its boiling point is 4371 °C (7900 °F). Zirconium has an electronegativity of 1.33 on the Pauling scale. Of the elements within d-block, zirconium has the fourth lowest electronegativity after yttrium, lutetium and hafnium.
At room temperature zirconium exhibits a hexagonally close packed crystal structure, α-Zr, which changes to β-Zr a body-centered cubic crystal structure at 863 °C. Zirconium exists in the β-phase until the melting point.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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