Page "Thulium" Paragraph 14

Naturally occurring thulium is composed of one stable isotope, Tm-169 ( 100 % natural abundance ).

Thirty one radioisotopes have been characterized, with the most stable being Tm-171 with a half-life of 1. 92 years, Tm-170 with a half-life of 128. 6 days, Tm-168 with a half-life of 93. 1 days, and Tm-167 with a half-life of 9. 25 days.

All of the remaining radioactive isotopes have half-lives that are less than 64 hours, and the majority of these have half-lives that are less than 2 minutes.

This element also has 14 meta states, with the most stable being Tm-164m ( t < sub > ½ </ sub > 5. 1 minutes ), Tm-160m ( t < sub > ½ </ sub > 74. 5 seconds ) and Tm-155m ( t < sub > ½ </ sub > 45 seconds ).