| yttrium | <chemistry> A rare metallic element of the boron-aluminium group, found in gadolinite and other rare minerals, and extracted as a dark gray powder. Symbol Y. Atomic weight. Alternative forms: ittrium. Associated with yttrium are certain rare elements, as erbium, ytterbium, samarium, etc, which are separated in a pure state with great difficulty. They are studied by means of their spark or phosphorescent spectra. Yttrium is now regarded as probably not a simple element, but as a mixture of several substances. Origin: NL, from Ytterby, in Sweden. See Erbium. Source: Websters Dictionary (01 Mar 1998) |
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| yttrium isotopes | Stable yttrium atoms that have the same atomic number as the element yttrium, but differ in atomic weight. Y-89 is the only naturally occurring stable isotope of yttrium. (12 Dec 1998) |
| yttrium radioisotopes | Unstable isotopes of yttrium that decay or disintegrate emitting radiation. Y atoms with atomic weights 82-88 and 90-96 are radioactive yttrium isotopes. (12 Dec 1998) |
| yttrium-90 | An artificial radioactive isotope with a physical half-life of 2.67 days which decays with the emission of a 2.282 Mev b particle; used as an implant in pituitary ablation. (05 Mar 2000) |