Gadolinium

Gadolinium is a silvery rare-earth metal with atomic number 64. Its strong magnetic response and ability to absorb neutrons make it useful in imaging, materials, and nuclear applications.

Gadolinium-based contrast agent: A compound containing gadolinium that improves contrast in magnetic resonance imaging. These agents use gadolinium’s magnetic properties to make tissues more distinguishable in MRI.
Lanthanide contraction: The gradual decrease in atomic and ionic size across the lanthanide series as nuclear charge increases. It helps explain gadolinium’s atomic dimensions and similarities to neighboring rare-earth elements.
Chemical element: A pure substance defined by atoms with the same number of protons. Gadolinium is the element whose atoms all contain 64 protons.
Johan Gadolin: A Finnish chemist and mineralogist whose work helped establish the study of rare-earth elements. Gadolinium was named in honor of Gadolin, though he did not discover the element.
Magnetic refrigeration: A cooling method that uses changes in a material’s temperature under an applied magnetic field. Gadolinium’s strong magnetocaloric effect makes it a model material for magnetic cooling.
4f electron: An electron occupying a 4f atomic orbital, characteristic of the lanthanide elements. Gadolinium’s unpaired 4f electrons contribute to its magnetic behavior.
Lanthanide: A series of 15 metallic elements from lanthanum through lutetium, including gadolinium. Gadolinium’s chemistry and placement follow the characteristic patterns of the lanthanides.
Paul-Émile Lecoq de Boisbaudran: A French chemist who identified gadolinium spectroscopically in 1880. His spectral observations first revealed the element in a mineral sample.
Magnetocaloric effect: A temperature change in a magnetic material caused by changing its magnetic field. This effect explains gadolinium’s use in magnetic refrigeration.
Hund's rules: Rules predicting the lowest-energy arrangement of electrons in partially filled atomic subshells. They account for gadolinium’s stable half-filled 4f subshell and large magnetic moment.

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