Osmium has seven naturally occurring isotopes, five of which are stable: ¹⁸⁷Os, ¹⁸⁸Os, ¹⁸⁹Os, ¹⁹⁰Os, and ¹⁹²Os. The other natural isotopes, ¹⁸⁴Os, and ¹⁸⁶Os, have extremely long half-life and for practical purposes can be considered to be stable... Wikipedia