Isotopes of scandium

Naturally-occurring scandium (₂₁Sc) is composed of one stable isotope, ⁴⁵Sc. Twenty-six radioisotopes have been characterized from ³⁷Sc to ⁶³Sc, with the most stable being ⁴⁶Sc with a half-life of 83.76 days, ⁴⁷Sc with a half-life of 3.3492 days, ⁴⁸Sc at 43.67 hours, ⁴⁴Sc at 4.042 hours, and ⁴³Sc at 3.891 hours. All other radioisotopes isotopes have half-lives shorter than an hour, and the majority of these shorter than 15 seconds. This element also has 13 meta states with the most stable being ^44m3Sc (t_1/2 = 58.6 h); this is the lightest isotope with a long-lived isomer.

The primary decay mode at masses lower than the only stable isotope, ⁴⁵Sc, is beta-plus or electron capture, and the primary mode at masses above it is beta-minus. The primary decay products at atomic weights below ⁴⁵Sc are calcium isotopes and the primary products from higher atomic weights are titanium isotopes.

Scandium-44 has potential medical use for PET imaging.