Isotopes of tungsten

Naturally occurring tungsten (₇₄W) consists of five isotopes. Four are considered stable (¹⁸²W, ¹⁸³W, ¹⁸⁴W, and ¹⁸⁶W) and one is slightly radioactive, ¹⁸⁰W, with an extremely long half-life of 1.8 ± 0.2 exayears (10¹⁸ years). On average, two alpha decays of ¹⁸⁰W occur per gram of natural tungsten per year, so for most practical purposes, ¹⁸⁰W can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only ¹⁸⁰W has been observed to do so. The other naturally occurring isotopes have not been observed to decay (they are observationally stable), and lower bounds for their half-lives have been established:

¹⁸²W, t_1/2 > 7.7×10²¹ years

¹⁸³W, t_1/2 > 4.1×10²¹ years

¹⁸⁴W, t_1/2 > 8.9×10²¹ years

¹⁸⁶W, t_1/2 > 8.2×10²¹ years

Thirty-four artificial radioisotopes of tungsten have been characterized with mass numbers ranging from 156 to 194, the most stable of which are ¹⁸¹W with a half-life of 121.2 days, ¹⁸⁵W with a half-life of 75.1 days, ¹⁸⁸W with a half-life of 69.4 days and ¹⁷⁸W with a half-life of 21.6 days. All of the remaining radioactive isotopes have half-lives of less than 24 hours, and most of these have half-lives that are less than 8 minutes. Tungsten also has 11 meta states with mass numbers of 158, 179, with 3, 180, with 2, 183, 185, 186, with 2, and 190, the most stable being ^179m1W (t_1/2 6.4 minutes).