Editing Gadolinium (section)

{{for|the advanced persistent threat known as GADOLINIUM in cybersecurity|APT40}}
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{{Infobox gadolinium}}
'''Gadolinium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Gd''' and [[atomic number]] 64. It is a silvery-white metal when oxidation is removed. Gadolinium is a malleable and [[ductile]] [[rare-earth element]]. It reacts with atmospheric oxygen or moisture slowly to form a black coating. Gadolinium below its [[Curie point]] of {{convert|20|C}} is [[ferromagnetism|ferromagnetic]], with an attraction to a magnetic field higher than that of nickel. Above this temperature it is the most [[paramagnetism|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.

Gadolinium was discovered in 1880 by [[Jean Charles Galissard de Marignac|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 [[Félix Trombe]] in 1935.

Gadolinium possesses unusual [[metallurgy|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 [[neutron]]s and is, therefore, used sometimes for shielding in [[neutron radiography]] and in [[nuclear reactor]]s.

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

Gadolinium(III) ions in water-soluble salts are highly toxic to mammals. However, [[chelation|chelated]] gadolinium(III) compounds prevent the gadolinium(III) from being exposed to the organism, and the majority is excreted by healthy<ref>{{cite journal | last1 = Donnelly | first1 = L. | last2 = Nelson | first2 = R. | year = 1998 | title = Renal excretion of gadolinium mimicking calculi on non-contrast CT | url = | journal = Pediatric Radiology | volume = 28 | issue = 6| page = 417 | doi = 10.1007/s002470050374 | pmid = 9634454 }}</ref> kidneys before it can deposit in tissues. Because of its [[paramagnetism|paramagnetic]] properties, solutions of chelated [[organic chemistry|organic]] gadolinium [[coordination complex|complexes]] are used as intravenously administered [[gadolinium-based MRI contrast agent]]s in medical [[magnetic resonance imaging]].

The main uses of gadolinium, in addition to use as a [[MRI contrast agent|contrast agent for MRI scans]], are in nuclear reactors, in alloys, as a phosphor in medical imaging, as a gamma ray emitter, in electronic devices, in optical devices, and in superconductors.