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Gadolinium

physical science Maturity 11-13 Next article →

Gadolinium is a silvery-white chemical element with the symbol Gd and atomic number 64. It belongs to the lanthanide series, which is a group of rare-earth elements. As a metal, it is both malleable and ductile, meaning it can be easily shaped or drawn into wires. While it is quite stable in dry air, it reacts with moisture to form a black oxide coating. This coating often spalls off, which exposes more of the metal to oxidation. In nature, gadolinium is never found in its pure metallic form. Instead, it exists only in oxidized forms within various minerals.

Gadolinium-2
Gadolinium-2

The magnetic properties of gadolinium are particularly unusual. Below a specific temperature known as its Curie point, the element is ferromagnetic. In this state, it is attracted to magnetic fields even more strongly than nickel. Once it rises above this temperature, it becomes paramagnetic. This means it is weakly attracted to magnetic fields. At human body temperature, gadolinium actually exhibits the greatest paramagnetic effect of any known element. It also demonstrates a magnetocaloric effect. This process causes the metal's temperature to increase when it enters a magnetic field and decrease when it leaves one.

Gadolinitas
Gadolinitas

Chemically, gadolinium is a strong reducing agent. This means it can reduce the oxides of several other metals back into their elemental forms. It is also quite electropositive. It reacts slowly when placed in cold water, but it reacts quite quickly with hot water to form gadolinium(III) hydroxide. In most of its chemical compounds, gadolinium adopts an oxidation state of +3. It can also form trivalent ions that possess fluorescent properties. These ions are used as phosphors in various technological applications. However, gadolinium(III) ions in water-soluble salts are highly toxic to mammals if they are not handled carefully.

To use gadolinium in medicine, scientists use a process called chelation. They create chelated organic gadolinium complexes to prevent the metal from being exposed to the body. These complexes are administered intravenously as contrast agents for Magnetic Resonance Imaging, or MRI. Because of its paramagnetic nature, the gadolinium helps increase nuclear spin relaxation rates. This makes the resulting medical images much clearer for doctors to read. This specialized use allows the element to be safe for patients while providing vital diagnostic information.

The history of gadolinium involves several important scientists and discoveries. The element is named after the mineral gadolinite. This mineral was named in honor of the Finnish chemist Johan Gadolin, who analyzed it in 1794. In 1880, the Swiss chemist Jean Charles de Marignac detected the element using spectroscopy. He initially gave it the provisional symbol Yα after observing spectral lines in samples of cerite. In 1886, the French chemist Paul-Émile Lecoq de Boisbaudran officially named it gadolinium. It took several more decades before the chemist Félix Trombe successfully isolated pure gadolinium in 1935.

Gadolinium is highly valued in nuclear science due to its ability to absorb neutrons. Specifically, the isotope gadolinium-157 has a very high thermal-neutron capture cross-section. This measurement is about 259,000 barns. Only the radioactive isotope xenon-135 has a higher capture cross-section. Because of this ability, gadolinium is used for shielding in neutron radiography and in nuclear reactors. It can even serve as a secondary, emergency shut-down measure in certain reactor types, such as CANDU reactors. It is also used in nuclear marine propulsion systems as a burnable poison.

Beyond nuclear and medical uses, gadolinium has significant metallurgical and electronic applications. It possesses unique properties that can improve other metals. For example, adding as little as 1% gadolinium can significantly improve the workability of iron and chromium. It also increases their resistance to oxidation at high temperatures. The element is also used in the production of alloys, electronic devices, and superconductors. It can even be incorporated into carbon nanotubes or encapsulated in fullerene molecules. These various roles show how a rare element can impact many different scientific fields.

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