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definition - Tungsten-181

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Isotopes of tungsten

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Naturally occurring tungsten (W) consists of five isotopes whose half-lives are so long that they can be considered stable. All can decay into isotopes of element 72 (hafnium) by alpha emission; 180W has been observed to have a half life of 1.8 +- 0.2 Ea (1018 years). The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be: 182W, T1/2 > 8.3 Ea; 184W, T1/2 > 29 Ea; 185W, T1/2 > 13 Ea; 186W, T1/2 > 27 Ea. [1] On average, two alpha decays of 180W occur in one gram of natural tungsten per year.

27 artificial radioisotopes of tungsten have been characterized, 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 4 meta states, the most stable being 179mW (t½ 6.4 minutes).

Standard atomic mass: 183.84(1) u


isotopic mass (u)
(mole fraction)
range of natural
(mole fraction)
excitation energy
158W7484157.97456(54)#1.37(17) ms0+
158mW1889(8) keV143(19) µs8+
159W7485158.97292(43)#8.2(7) ms7/2-#
160W7486159.96848(22)90(5) ms0+
161W7487160.96736(21)#409(16) ms7/2-#
162W7488161.963497(19)1.36(7) s0+
163W7489162.96252(6)2.8(2) s3/2-#
164W7490163.958954(13)6.3(2) s0+
165W7491164.958280(27)5.1(5) s3/2-#
166W7492165.955027(11)19.2(6) s0+
167W7493166.954816(21)19.9(5) s3/2-#
168W7494167.951808(17)51(2) s0+
169W7495168.951779(17)76(6) s(5/2-)
170W7496169.949228(16)2.42(4) min0+
171W7497170.94945(3)2.38(4) min(5/2-)
172W7498171.94729(3)6.6(9) min0+
173W7499172.94769(3)7.6(2) min5/2-
174W74100173.94608(3)33.2(21) min0+
175W74101174.94672(3)35.2(6) min(1/2-)
176W74102175.94563(3)2.5(1) h0+
177W74103176.94664(3)132(2) min1/2-
178W74104177.945876(16)21.6(3) d0+
179W74105178.947070(17)37.05(16) min(7/2)-
179m1W221.926(8) keV6.40(7) min(1/2)-
179m2W1631.90(8) keV390(30) ns(21/2+)
179m3W3348.45(16) keV750(80) ns(35/2-)
180W74106179.946704(4)STABLE [>700E+15 a]0+0.0012(1)
180m1W1529.04(3) keV5.47(9) ms8-
180m2W3264.56(21) keV2.33(19) µs14-
181W74107180.948197(5)121.2(2) d9/2+
182W74108181.9482042(9)STABLE [>170E+18 a]0+0.2650(16)
183W74109182.9502230(9)STABLE [>80E+18 a]1/2-0.1431(4)
183mW309.493(3) keV5.2(3) s11/2+
184W74110183.9509312(9)STABLE [>180E+18 a]0+0.3064(2)
185W74111184.9534193(10)75.1(3) d3/2-
185mW197.43(5) keV1.597(4) min11/2+
186W74112185.9543641(19)STABLE [>4.1E+18 a]0+0.2843(19)
186m1W1517.2(6) keV18(1) µs(7-)
186m2W3542.8(21) keV>3 ms(16+)
187W74113186.9571605(19)23.72(6) h3/2-
188W74114187.958489(4)69.78(5) d0+
189W74115188.96191(21)11.6(3) min(3/2-)
190W74116189.96318(18)30.0(15) min0+
190mW2381(5) keV<3.1 ms(10-)
191W74117190.96660(21)#20# s [>300 ns]3/2-#
192W74118191.96817(64)#10# s [>300 ns]0+


  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.


  1. ^ National Nuclear Data Center table of nuclides, http://www.nndc.bnl.gov/chart/

Isotopes of tantalumIsotopes of tungstenIsotopes of rhenium
Index to isotope pages · Table of nuclides


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