Isotopes of tungsten

(Redirected from Tungsten-186)

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:

Isotopes of tungsten (74W)
Main isotopesDecay
abun­dancehalf-life (t1/2)modepro­duct
180W0.120%1.8×1018 yα176Hf
181Wsynth121.2 dε181Ta
182W26.5%stable
183W14.3%stable
184W30.6%stable
185Wsynth75.1 dβ185Re
186W28.4%stable
188Wsynth69.78 dβ188Re
Standard atomic weight Ar°(W)
182W, t1/2 > 7.7×1021 years
183W, t1/2 > 4.1×1021 years
184W, t1/2 > 8.9×1021 years
186W, t1/2 > 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 (t1/2 6.4 minutes).

List of isotopes

Nuclide
[n 1]
ZNIsotopic mass (Da)
[n 2][n 3]
Half-life
[n 4][n 5]
Decay
mode

[n 6]
Daughter
isotope

[n 7][n 8]
Spin and
parity
[n 9][n 5]
Natural abundance (mole fraction)
Excitation energyNormal proportionRange of variation
156W[3]7482157+57
−34
 ms
β+156Ta0+
157W[4]7483275(40) msβ+157Ta(7/2−)
158W7484157.97456(54)#1.37(17) msα154Hf0+
158mW1889(8) keV143(19) μsα154Hf8+
159W7485158.97292(43)#8.2(7) msα (82%)155Hf7/2−#
β+ (18%)159Ta
160W7486159.96848(22)90(5) msα (87%)156Hf0+
β+ (14%)160Ta
161W7487160.96736(21)#409(16) msα (73%)157Hf7/2−#
β+ (23%)161Ta
162W7488161.963497(19)1.36(7) sβ+ (53%)162Ta0+
α (47%)158Hf
163W7489162.96252(6)2.8(2) sβ+ (59%)163Ta3/2−#
α (41%)159Hf
164W7490163.958954(13)6.3(2) sβ+ (97.4%)164Ta0+
α (2.6%)160Hf
165W7491164.958280(27)5.1(5) sβ+ (99.8%)165Ta3/2−#
α (.2%)161Hf
166W7492165.955027(11)19.2(6) sβ+ (99.96%)166Ta0+
α (.035%)162Hf
167W7493166.954816(21)19.9(5) sβ+ (>99.9%)167Ta3/2−#
α (<.1%)163Hf
168W7494167.951808(17)51(2) sβ+ (99.99%)168Ta0+
α (.0319%)164Hf
169W7495168.951779(17)76(6) sβ+169Ta(5/2−)
170W7496169.949228(16)2.42(4) minβ+(99%)170Ta0+
α (1%)166Hf
171W7497170.94945(3)2.38(4) minβ+171Ta(5/2−)
172W7498171.94729(3)6.6(9) minβ+172Ta0+
173W7499172.94769(3)7.6(2) minβ+173Ta5/2−
174W74100173.94608(3)33.2(21) minβ+174Ta0+
175W74101174.94672(3)35.2(6) minβ+175Ta(1/2−)
176W74102175.94563(3)2.5(1) hEC176Ta0+
177W74103176.94664(3)132(2) minβ+177Ta1/2−
178W74104177.945876(16)21.6(3) dEC178Ta0+
179W74105178.947070(17)37.05(16) minβ+179Ta(7/2)−
179m1W221.926(8) keV6.40(7) minIT (99.72%)179W(1/2)−
β+ (.28%)179Ta
179m2W1631.90(8) keV390(30) ns(21/2+)
179m3W3348.45(16) keV750(80) ns(35/2−)
180W[n 10]74106179.946704(4)1.8(0.2)×1018 yα176Hf0+0.0012(1)
180m1W1529.04(3) keV5.47(9) msIT180W8−
180m2W3264.56(21) keV2.33(19) μs14−
181W74107180.948197(5)121.2(2) dEC181Ta9/2+
182W74108181.9482042(9)Observationally Stable[n 11]0+0.2650(16)
183W74109182.9502230(9)Observationally Stable[n 12]1/2−0.1431(4)
183mW309.493(3) keV5.2(3) sIT183W11/2+
184W74110183.9509312(9)Observationally Stable[n 13]0+0.3064(2)
185W74111184.9534193(10)75.1(3) dβ185Re3/2−
185mW197.43(5) keV1.597(4) minIT185W11/2+
186W74112185.9543641(19)Observationally Stable[n 14]0+0.2843(19)
186m1W1517.2(6) keV18(1) μs(7−)
186m2W3542.8(21) keV>3 ms(16+)
187W74113186.9571605(19)23.72(6) hβ187Re3/2−
188W74114187.958489(4)69.78(5) dβ188Re0+
189W74115188.96191(21)11.6(3) minβ189Re(3/2−)
190W74116189.96318(18)30.0(15) minβ190Re0+
190mW2381(5) keV<3.1 ms(10−)
191W74117190.96660(21)#20# s
[>300 ns]
3/2−#
192W74118191.96817(64)#10# s
[>300 ns]
0+
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References