Zirconium is a chemical element ; it has symbol Zr and atomic number 40. The name zirconium is derived from the name of the mineral zircon , the most important source of zirconium. The word is related to Persian zargun (zircon; zar-gun , "gold-like" or "as gold").[8] It is a lustrous , grey-white, strong transition metal that closely resembles hafnium and, to a lesser extent, titanium .
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Zirconium, 40 Zr Pronunciation (zur-KOH -nee-əm ) Appearance silvery white
Atomic number (Z ) 40 Group group 4 Period period 5 Block d-block Electron configuration [ Kr ] 4d2 5s2 Electrons per shell 2, 8, 18, 10, 2 Phase at STP solid Melting point 2125 K (1852 °C, 3365 °F) Boiling point 4650 K (4377 °C, 7911 °F) Density (at 20° C) 6.505 g/cm3 [3] when liquid (at m.p. ) 5.8 g/cm3 Heat of fusion 14 kJ/mol Heat of vaporization 591 kJ/mol Molar heat capacity 25.36 J/(mol·K) Vapor pressure
P (Pa)
1
10
100
1 k
10 k
100 k
at T (K)
2639
2891
3197
3575
4053
4678
Oxidation states −2, 0, +1,[4] [ citation needed ] +2, +3, +4 (an amphoteric oxide) Electronegativity Pauling scale: 1.33 Ionization energies 1st: 640.1 kJ/mol 2nd: 1270 kJ/mol 3rd: 2218 kJ/mol Atomic radius empirical: 160 pm Covalent radius 175±7 pm Spectral lines of zirconiumNatural occurrence primordial Crystal structure hexagonal close-packed (hcp) (hP2 )Lattice constants a = 323.22 pmc = 514.79 pm (at 20 °C)[3] Thermal expansion 5.69× 10−6 /K (at 20 °C)[3] [lower-alpha 1] Thermal conductivity 22.6 W/(m⋅K) Electrical resistivity 421 nΩ⋅m (at 20 °C) Magnetic ordering paramagnetic [5] Young's modulus 88 GPa Shear modulus 33 GPa Bulk modulus 91.1 GPa Speed of sound thin rod 3800 m/s (at 20 °C) Poisson ratio 0.34 Mohs hardness 5.0 Vickers hardness 820–1800 MPa Brinell hardness 638–1880 MPa CAS Number 7440-67-7 Naming after zircon , zargun زرگون meaning "gold-colored". Discovery Martin Heinrich Klaproth (1789)First isolation Jöns Jakob Berzelius (1824)
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Zirconium forms a variety of inorganic and organometallic compounds such as zirconium dioxide and zirconocene dichloride , respectively. Five isotopes occur naturally, four of which are stable.
Zirconium is mainly used as a refractory and opacifier , although small amounts are used as an alloying agent for its strong resistance to corrosion. Zirconium compounds have no known biological role.