Gadolinium
Rare-earth element used in MRI contrast agents and nuclear shielding.
Gadolinium is a chemical element with the symbol Gd and atomic number 64, classified as a silvery-white, ductile, and malleable rare-earth metal. In its pure, unoxidized state, it exhibits this metallic luster, but it slowly reacts with atmospheric oxygen and moisture to form a black oxide coating. Below its Curie point, it is ferromagnetic, displaying a stronger attraction to magnetic fields than nickel; above this temperature, it becomes the most paramagnetic element known. In nature, gadolinium is found only in oxidized forms, and when separated, it typically contains impurities of other rare earths due to their similar chemical properties.
The element was discovered in 1880 by Jean Charles de Marignac, who identified its oxide using spectroscopy. It was named after the mineral gadolinite, which itself honors the Finnish chemist Johan Gadolin. Pure gadolinium was first isolated in 1935 by Félix Trombe. Metallurgically, even a 1% addition of gadolinium can significantly improve the workability and high-temperature oxidation resistance of metals like iron and chromium. As a metal or salt, it absorbs neutrons, making it useful for shielding in neutron radiography and nuclear reactors. Gadolinium forms trivalent ions with fluorescent properties, and its salts serve as phosphors. While water-soluble gadolinium(III) ions are highly toxic to mammals, chelated compounds prevent exposure to the organism, and most are excreted by healthy kidneys. These paramagnetic chelated complexes are used intravenously as contrast agents in medical MRI scans. Additional applications include use in alloys, electronic and optical devices, superconductors, and as a gamma ray emitter.
- symbol
- Gd
- atomic_number
- 64
- discovered_by
- Jean Charles de Marignac
- first_isolated_by
- Félix Trombe
- named_after
- mineral gadolinite (named for Johan Gadolin)
Lore & Background
He designated the element with the provisional symbol Yα. Gadolinium is a member of the lanthanide series, with electron configuration [Xe]4f75d16s2. Gadolinium exhibits a magnetocaloric effect, and its compounds are used in phosphors and as MRI contrast agents due to paramagnetic properties. Naturally occurring gadolinium consists of six stable isotopes and the primordial radionuclide 152Gd, which has an extremely long half-life of 1.08×10^14 years. The element is found in minerals such as monazite and bastnäsite, and it is too reactive to exist in native form. Gadolinium metal is relatively stable in dry air but tarnishes in moist air, forming a loosely-adhering oxide coating.
Reader's Guide
Gadolinium's significance stems from its combination of magnetic, nuclear, and metallurgical properties. Below its Curie point of 20 °C, it is ferromagnetic with a magnetic attraction higher than nickel; above that, it is the most paramagnetic element, making it essential for MRI contrast agents. Chelated gadolinium(III) compounds are used intravenously in medical imaging because they are paramagnetic and, when chelated, are excreted by healthy kidneys before depositing in tissues. In nuclear reactors, gadolinium's high neutron capture cross-section (especially 157Gd) makes it valuable for shielding and control rods. As little as 1% gadolinium improves the workability and oxidation resistance of iron, chromium, and related metals at high temperatures. Gadolinium also serves as a phosphor in medical imaging, a gamma ray emitter, and in electronic, optical, and superconducting devices. The element's toxicity in ionic form is mitigated by chelation, allowing safe medical use. Overall, gadolinium bridges fundamental physics, materials science, and practical medical technology.
Did You Know?
- Gadolinium is ferromagnetic below 20 °C and the most paramagnetic element above that temperature.
- As little as 1% gadolinium can significantly improve the workability and resistance to oxidation at high temperatures of iron, chromium, and related metals.
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