GadoliniumIII

Gadolinium(III) is the most stable oxidation state of the element gadolinium, a lanthanide metal belonging to the f-block of the periodic table. In this state gadolinium exists as the trivalent ion Gd³⁺, which is formed by the loss of three electrons from the neutral atom. The resulting ion has a 4f⁷ electronic configuration, giving it a half‑filled f-shell that contributes to its characteristic magnetic properties.

The Gd³⁺ ion has a crystal field splitting energy that is relatively weak compared to other lanthanides, so its 4f electrons are largely shielded by filled 5s and 5p orbitals. This shielding results in a high magnetic moment (seven unpaired electrons) and a small ionic radius of 93.8 pm for coordination number eight. The ion usually forms octahedral or cubic complexes with ligands capable of coordination via oxygen, nitrogen, or sulfur donors, and it exhibits a strong propensity for forming charged salts such as gadolinium(III) sulfate or perchlorate.

In practical applications, gadolinium(III) salts serve as contrast agents in magnetic resonance imaging (MRI). Gadolinium chelates, such as gadopentetate dimeglumine, are engineered to complex the Gd³⁺ ion, reducing its paramagnetic relaxation rate while keeping it biologically inert. The high magnetic susceptibility of the ion enhances proton relaxation times in nearby water molecules, thereby improving image contrast. Other uses of Gd³⁺ include the manufacturing of phosphors for display technologies, the creation of greenish luminescent compounds in LEDs, and as a dopant in other materials to modify optical and magnetic behavior.

Because of its strong magnetic moment and chemical reactivity, handling Gd³⁺ compounds requires precautionary measures to avoid exposure to uncomplexed salts. In aqueous solutions, Gd³⁺ can precipitate as gadolinium hydroxide or carbonate, so it is often supplied in soluble complex forms. The ion’s role in medical imaging, phosphors, and other advanced materials underscores its importance in both scientific research and commercial technology.