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Gadolinium

Chemical element, symbol Gd and atomic number 64 / From Wikipedia, the free encyclopedia

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Gadolinium is a chemical element; it has symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is a malleable and ductile rare-earth element. Gadolinium reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its Curie point of 20 °C (68 °F) is ferromagnetic, with an attraction to a magnetic field higher than that of nickel. Above this temperature it is the most paramagnetic element. It is found in nature only in an oxidized form. When separated, it usually has impurities of the other rare-earths because of their similar chemical properties.

Quick facts: Gadolinium, Pronunciation, Appearance, Standa...
Gadolinium, 64Gd
Gadolinium-4.jpg
Gadolinium
Pronunciation/ˌɡædəˈlɪniəm/ (GAD-ə-LIN-ee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Gd)
Gadolinium in the periodic table


Gd

Cm
europiumgadoliniumterbium
Atomic number (Z)64
Groupf-block groups (no number)
Periodperiod 6
Block  f-block
Electron configuration[Xe] 4f7 5d1 6s2
Electrons per shell2, 8, 18, 25, 9, 2
Physical properties
Phase at STPsolid
Melting point1585 K (1312 °C, 2394 °F)
Boiling point3546 K (3273 °C, 5923 °F)
Density (near r.t.)7.90 g/cm3
when liquid (at m.p.)7.4 g/cm3
Heat of fusion10.05 kJ/mol
Heat of vaporization301.3 kJ/mol
Molar heat capacity37.03 J/(mol·K)
Vapor pressure (calculated)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1836 2028 2267 2573 2976 3535
Atomic properties
Oxidation states0,[3] +1, +2, +3 (a mildly basic oxide)
ElectronegativityPauling scale: 1.20
Ionization energies
  • 1st: 593.4 kJ/mol
  • 2nd: 1170 kJ/mol
  • 3rd: 1990 kJ/mol
Atomic radiusempirical: 180 pm
Covalent radius196±6 pm
Color lines in a spectral range
Spectral lines of gadolinium
Other properties
Natural occurrenceprimordial
Crystal structure hexagonal close-packed (hcp)
Hexagonal close packed crystal structure for gadolinium
Thermal expansionα poly: 9.4 µm/(m⋅K) (at 100 °C)
Thermal conductivity10.6 W/(m⋅K)
Electrical resistivityα, poly: 1.310 µΩ⋅m
Magnetic orderingferromagneticparamagnetic transition at 293.4 K
Molar magnetic susceptibility+755000.0×10−6 cm3/mol (300.6 K)[4]
Young's modulusα form: 54.8 GPa
Shear modulusα form: 21.8 GPa
Bulk modulusα form: 37.9 GPa
Speed of sound thin rod2680 m/s (at 20 °C)
Poisson ratioα form: 0.259
Vickers hardness510–950 MPa
CAS Number7440-54-2
History
Namingafter the mineral gadolinite (itself named after Johan Gadolin)
DiscoveryJean Charles Galissard de Marignac (1880)
First isolationLecoq de Boisbaudran (1886)
Isotopes of gadolinium
Main isotopes[5] Decay
abun­dance half-life (t1/2) mode pro­duct
148Gd synth 86.9 y[6] α 144Sm
150Gd synth 1.79×106 y α 146Sm
152Gd 0.2% 1.08×1014 y α 148Sm
153Gd synth 240.6 d ε 153Eu
154Gd 2.18% stable
155Gd 14.8% stable
156Gd 20.5% stable
157Gd 15.7% stable
158Gd 24.8% stable
160Gd 21.9% stable
Symbol_category_class.svg Category: Gadolinium
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Gadolinium was discovered in 1880 by Jean Charles de Marignac, who detected its oxide by using spectroscopy. It is named after the mineral gadolinite, one of the minerals in which gadolinium is found, itself named for the Finnish chemist Johan Gadolin. Pure gadolinium was first isolated by the chemist Paul-Émile Lecoq de Boisbaudran around 1886.

Gadolinium possesses unusual metallurgical properties, to the extent that as little as 1% of gadolinium can significantly improve the workability and resistance to oxidation at high temperatures of iron, chromium, and related metals. Gadolinium as a metal or a salt absorbs neutrons and is, therefore, used sometimes for shielding in neutron radiography and in nuclear reactors.

Like most of the rare earths, gadolinium forms trivalent ions with fluorescent properties, and salts of gadolinium(III) are used as phosphors in various applications.

Gadolinium(III) ions in water-soluble salts are highly toxic to mammals. However, chelated gadolinium(III) compounds prevent the gadolinium(III) from being exposed to the organism and the majority is excreted by healthy[7] kidneys before it can deposit in tissues. Because of its paramagnetic properties, solutions of chelated organic gadolinium complexes are used as intravenously administered gadolinium-based MRI contrast agents in medical magnetic resonance imaging.

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