Gadolinium
In 1880, Swiss chemist Jean Charles de Marignac observed distinct spectroscopic lines in samples of gadolinite. He detected the oxide of a new element using this method on minerals from Finland and Sweden. The mineral itself had been named earlier by Martin Klaproth to honor Finnish chemist Johan Gadolin. Gadolin had first analyzed that specific ore in 1794 near the town of Ytterby. De Marignac eventually separated a mineral oxide from cerite which contained far more of the element than gadolinite did. He assigned it the provisional symbol Yα before Paul-Émile Lecoq de Boisbaudran officially named it gadolinium in 1886. Pure metal remained elusive until Félix Trombe isolated it in 1935.
Gadolinium possesses 64 electrons arranged in the configuration [Xe]4f75d16s2. This arrangement allows three valence electrons while keeping four f-electrons strongly bound to the nucleus. At room temperature the metal crystallizes into a hexagonal close-packed α-form structure. Temperatures above 293 kelvins transform it into a body-centered cubic β-form. Below its Curie point of 293 kelvins, the element exhibits ferromagnetic properties stronger than nickel. Above that same temperature threshold, it becomes the most paramagnetic element known. Individual atoms can be encapsulated inside fullerene molecules for visualization under transmission electron microscopes. Scientists have also incorporated small clusters of Gd atoms into carbon nanotubes.
Mining operations extract crushed minerals like monazite and bastnäsite using hydrochloric acid or sulfuric acid. These acids convert insoluble oxides into soluble chlorides or sulfates for further processing. Chemists partially neutralize acidic filtrates with caustic soda to reach pH levels between 3 and 4. Thorium precipitates as hydroxide during this step and is removed from the solution. Ammonium oxalate converts remaining rare earths into insoluble oxalates which are then heated into oxides. Nitric acid dissolves these oxides while excluding cerium whose oxide remains insoluble in HNO3. Magnesium nitrate produces crystallized double salts containing gadolinium alongside samarium and europium. Ion exchange chromatography separates these rare-earth ions before a complexing agent washes them out selectively. Pure metal finally emerges by heating the oxide with calcium at 1200 degrees Celsius within an argon atmosphere.
Solutions of organic gadolinium complexes serve as intravenous contrast agents for magnetic resonance imaging procedures. Magnevist stands as the most widespread example used globally today. Paramagnetic ions increase nuclear spin relaxation rates to enhance image clarity in medical scans. Gadonanotubes packed with gadolinium offer forty times greater effectiveness than standard contrast agents. Brain tumors allow these agents to penetrate tissues where they facilitate detection via contrast-enhanced MRI. Delayed gadolinium-enhanced magnetic resonance imaging uses ionic compounds originally known as Magnevist to detect osteoarthritis. These agents enter proteoglycan-depleted cartilage based on electrostatic repulsion principles. About a dozen different Gd-chelated agents have received approval worldwide for clinical use. The toxicity of free gadolinium ions decreases by a factor of thirty-one when chelation occurs.
Gadolinium-157 holds the highest thermal-neutron capture cross-section among any stable nuclide at approximately 259,000 barns. This property makes it effective for shielding in neutron radiography and inside nuclear reactors. Some CANDU reactor types utilize gadolinium as a secondary emergency shut-down measure. Nuclear marine propulsion systems employ the element as a burnable poison to control reactions. Scientists investigate its use in neutron capture therapy to target specific tumors within patients. The isotope gadolinium-153 emits gamma radiation with strong peaks at 41 keV and 102 keV. Quality-assurance applications rely on this emission for line sources and calibration phantoms. Bone density gauges for osteoporosis screening also utilize these gamma-ray emissions from the isotope. Low-energy neutrons arising from antineutrino absorption are captured by gadolinium nuclei in Japan's Super-Kamiokande detector.
As little as one percent of gadolinium improves workability of iron and chromium alloys significantly. These alloys gain resistance to high temperatures and oxidation through the addition. Gadolinium yttrium garnet finds microwave applications while serving as substrate material for magneto-optical films. Solid oxide fuel cells utilize gadolinium-doped ceria to achieve high ionic conductivity at lower operating temperatures. Pure Gd exhibits a large magnetocaloric effect near its Curie temperature of 293 kelvins. Alloys like Gd5(SixGe1 minus x)4 allow scientists to adjust Curie temperatures by varying silicon and germanium compositions. Gadolinium barium copper oxide set a world record in 2014 trapping 17.6 teslas within bulk superconductors. This material shares an analogous chemical composition with yttrium barium copper oxide used in wind turbines. Green phosphors for color TV tubes once contained terbium-doped gadolinium oxysulfide emitting light at 540 nanometers.
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Common questions
Who discovered gadolinium and when was it officially named?
Jean Charles de Marignac observed distinct spectroscopic lines in 1880, but Paul-Émile Lecoq de Boisbaudran officially named the element gadolinium in 1886. Johan Gadolin first analyzed the specific ore from Ytterby near Finland in 1794.
What is the electron configuration of gadolinium and how does its structure change with temperature?
Gadolinium possesses 64 electrons arranged in the configuration [Xe]4f75d16s2. At room temperature the metal crystallizes into a hexagonal close-packed alpha-form structure, while temperatures above 293 kelvins transform it into a body-centered cubic beta-form.
How is pure gadolinium metal extracted from minerals like monazite and bastnäsite?
Mining operations extract crushed minerals using hydrochloric acid or sulfuric acid to convert insoluble oxides into soluble chlorides or sulfates. Pure metal finally emerges by heating the oxide with calcium at 1200 degrees Celsius within an argon atmosphere after ion exchange chromatography separates rare-earth ions.
Why are gadolinium complexes used as contrast agents for magnetic resonance imaging procedures?
Solutions of organic gadolinium complexes serve as intravenous contrast agents because paramagnetic ions increase nuclear spin relaxation rates to enhance image clarity. About a dozen different Gd-chelated agents have received approval worldwide for clinical use, and toxicity decreases by a factor of thirty-one when chelation occurs.
Which stable nuclide has the highest thermal-neutron capture cross-section and how is it used in reactors?
Gadolinium-157 holds the highest thermal-neutron capture cross-section among any stable nuclide at approximately 259,000 barns. Some CANDU reactor types utilize gadolinium as a secondary emergency shut-down measure while nuclear marine propulsion systems employ the element as a burnable poison to control reactions.
What industrial applications does gadolinium enable in alloys and superconductors?
As little as one percent of gadolinium improves workability of iron and chromium alloys significantly while Gadolinium barium copper oxide set a world record in 2014 trapping 17.6 teslas within bulk superconductors. Solid oxide fuel cells utilize gadolinium-doped ceria to achieve high ionic conductivity at lower operating temperatures.