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| Atomic symbol: Gd |
| Atomic number: 64 |
| Atomic weight: 157.25 |
| Atomic volume: 19.9 cm3/mol |
| Density: 7.895 g/cm3 |
| Period Number: 6 |
| Group number: none |
| Group name: Rare Earth, Lanthanides |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 1584.2 K |
| Boiling point: 3273 K |
| Heat of fusion: 10.050 kJ/mol |
| Heat of vaporization: 359.40 kJ/mol |
| Ionization Energy: 6.150 eV |
| 1st ionization energy: 592.6 kJ/mole |
| 2nd ionization energy: 1167 kJ/mole |
| 3rd ionization energy: 1991 kJ/mole |
| Electronegativity: 1.17 |
| Electron affinity: 50 kJ/mole |
| Specific heat: 0.23 J/gK |
| Heat atomization: 398 kJ/mole atoms |
| Shells: 2,8,18,25,9,2 |
| Electron Shell Configuration: [Xe] 4f7 5d1 6s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 3 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 3 |
Appearance & Characteristics |
| Structure:: hcp: hexagonal close pkd |
| Color: silvery-white |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: ? |
| Uses: alloys, CD disk |
| Reaction with air: vigorous, =>Gd2O3 |
| Reaction with 6M HCl: mild, =>H2, GdCl3 |
| Reaction with 15M HNO3: mild, =>Gd(NO3)3 |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 7 |
| Oxide(s): Gd2O3 |
| Hydride(s): GdH2 GdH3 |
| Chloride(s): GdCl3 |
| Atomic Radius: 180 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): pm |
| Ionic radius (3+ ion): 107.8 pm |
| Thermal conductivity: 10.5 J/m-sec-deg |
| Electrical conductivity: 7.9 1/mohm-cm |
| Polarizability: 23.5 A^3 |
| Source: Monazite(phosphate),bastnaesite |
| Relative abundance solar system: -0.481 log |
| Abundance earth's crust: 0.7 log |
| Estimated crustal abundance: 6.2 milligrams per kilogram |
| Estimated oceanic abundance: 7×10-7 milligrams per liter |
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| (From gadolinite, a mineral named for Gadolin, a Finnish chemist.) The rare earth metal is obtained from the mineral gadolinite. Gadolinia, the oxide of gadolinium, was separated by Marignac in 1880 and Lecoq de Boisbaudran independently isolated it from Mosander's yttria in 1886. |
| Gadolinium is found in several other minerals, including monazite and bastnasite, both of which are commercially important. With the development of ion-exchange and solvent extraction techniques, the availability and prices of gadolinium and the other rare-earth metals have greatly improved. The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium. |
As with other related rare-earth metals, gadolinium is silvery white, has a metallic luster, and is malleable and ductile. At room temperature, gadolinium crystallizes in the hexagonal, close-packed alpha form. Upon heating to 12350C, alpha gadolinium transforms into the beta form, which has a body-centered cubic structure.
The metal is relatively stable in dry air, but tarnishes in moist air and forms a loosely adhering oxide film which falls off and exposes more surface to oxidation. The metal reacts slowly with water and is soluble in dilute acid.
Gadolinium has the highest thermal neutron capture cross-section of any known element (49,000 barns).
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Gadolinium yttrium garnets are used in microwave applications and gadolinium compounds are used as phosphors in color television sets.
The metal has unusual superconductive properties. As little as 1 percent gadolinium improves the workability and resistance of iron, chromium, and related alloys to high temperatures and oxidation.
Gadolinium ethyl sulfate has extremely low noise characteristics and may find use in duplicating the performance of amplifiers, such as the maser.
The metal is ferromagnetic. Gadolinium is unique for its high magnetic movement and for its special Curie temperature (above which ferromagnetism vanishes) lying just at room temperature, meaning it could be used as a magnetic component that can sense hot and cold.
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| Natural gadolinium is a mixture of seven isotopes, but 17 isotopes of gadolinium are now recognized. Although two of these, 155Gd and 157Gd, have excellent capture characteristics, they are only present naturally in low concentrations. As a result, gadolinium has a very fast burnout rate and has limited use as a nuclear control rod material. |
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