Isotopes of terbium

Naturally occurring radioactive isotopes have half-lifes that are less than 6.907 days, and the majority of these have half lifes that are less than 24 seconds. This element also has 18 meta states, with the most stable being 156m1-Tb (t_½ 24.4 hours), 154m2-Tb (t_½ 22.7 hours) and 154m1-Tb (t_½ 9.4 hours).