Gadolinium is a chemical element that has the symbol Gd and atomic number 64.
Gadolinium is a silvery-white, malleable and ductile rare-earth metal with a metallic luster. It crystallizes in hexagonal, close-packed alpha form at room temperature, but, when heated to 1508 K or more, it transforms into its beta form, which has a body-centered cubic structure.
Unlike other rare earth elements, gadolinium is relatively stable in dry air. However, it tarnishes quickly in moist air and forms a loosely-adhering oxide that spalls off, and then exposes more surface to oxidation. Gadolinium reacts slowly with water, and it is soluble in dilute acids.
Gadolinium-157 has the highest thermal neutron capture cross-section of any known nuclide with the exception of Xenon-135, 49,000 barns, but it also has a fast burn-out rate, limiting its usefulness as a nuclear control rod material.
Gadolinium becomes superconductive below a critical temperature of 1.083 K. It is strongly paramagnetic at room temperature, and exhibits ferromagnetic properties below room temperature.
Gadolinium demonstrates a magnetocaloric effect whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field. The effect is considerably stronger for the gadolinium alloy Gd5(Si2Ge2).
|Atomic number||64||Melting point /°C||1312|
|No. of naturally occurring isotopes||7||Boiling point /°C||-3000|
|Atomic weight||157.25 (+/-3)||ΔHvap/kJmol-1||301|
|Outer electron configuration||4f7d46s2||ΔHf(monoatomic gas/kJmol-1||398|
|Metal radius(6-coordinate)/pm||180.4||ΔH(hydration Ln3+)/kJmol-1||3571|
|Ionic radius(6-coordinate)/pm III||93.8||Ionization energy/kJ mol-1 I||595|
|Ionic radius(6-coordinate)/pm II||-||Ionization energy/kJmol-1 II||1172|
|Electrical resistivity||Ionization energy/kJmol-1 III||1999|
|Temperature (oC) @Vap. Pressure||Techniques||Remarks|
|10-8 Torr||10-6 Torr||10-4 Torr||Electron Beam||Crucible||Coil||Boat|
|760||900||1175||Excellent||Al2O3||-||Tantalum||High Tantalum solubility.|
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