Actinides  Halflife  Fission products  

^{244}Cm  ^{241}Pu ^{f}  ^{250}Cf  ^{243}Cm^{f}  10–30 y  ^{137}Cs  ^{90}Sr  ^{85}Kr  
^{232}U ^{ f}  ^{238}Pu  f is for fissile 
69–90 y  ^{151}Sm nc➔  
4n  ^{249}Cf ^{f}  ^{242}Am^{f}  141–351  No fission
product has halflife 10^{2} to 2×10^{5} years 

^{241}Am  ^{251}Cf ^{f}  431–898  
^{240}Pu  ^{229}Th  ^{246}Cm  ^{243}Am  5–7 ky  
4n  ^{245}Cm^{f}  ^{250}Cm  ^{239}Pu ^{f}  8–24 ky  
^{233}U ^{ f}  ^{230}Th  ^{231}Pa  32–160  
4n+1  ^{234}U  4n+3  211–290  ^{99}Tc  ^{126}Sn  ^{79}Se  
^{248}Cm  ^{242}Pu  340–373  Longlived fission products  
^{237}Np  4n+2  1–2 my  ^{93}Zr  ^{135}Cs nc➔  
^{236}U  4n+1  ^{247}Cm^{f}  6–23  ^{107}Pd  ^{129}I  
^{244}Pu  80 my  >7%  >5%  >1%  >.1%  
^{232}Th  ^{238}U  ^{235}U ^{ f}  0.7–12by  fission product yield 
Uranium (U) is a naturally occurring element that has no stable isotopes but two primordial isotopes uranium238 and uranium235 that are radioactive with long halflife and are found in appreciable quantity in Earth's crust, along with the decay product uranium234. The average atomic mass of natural uranium is 238.02891(3) u. Other isotopes such as uranium232 have been produced in breeder reactors.
Historically, isotopes of uranium were known as
Naturally occurring uranium is composed of three major isotopes, uranium238 (99.28% natural abundance), uranium235 (0.71%), and uranium234 (0.0054%). All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium238 with a halflife of 4.51 × 10^{9} years (close to the age of the Earth), uranium235 with a halflife of 7.13 × 10^{8} years, and uranium234 with a halflife of 2.48 × 10^{5} years.^{[1]}
Uranium238 is an α emitter, decaying through the 18member uranium series into lead206.^{[2]} The constant rates of decay in these series makes comparison of the ratios of parent to daughter elements useful in radiometric dating. Uranium233 is made from thorium232 by neutron bombardment.
The isotope uranium235 is important for both nuclear reactors and nuclear weapons because it is the only isotope existing in nature to any appreciable extent that is fissile, that is, can be broken apart by thermal neutrons.^{[2]} The isotope uranium238 is also important because it absorbs neutrons to produce a radioactive isotope that subsequently decays to the isotope plutonium239, which also is fissile.
nuclide symbol 
Z(p)  N(n)  isotopic mass (u) 
halflife  nuclear spin 
representative isotopic composition (mole fraction) 
range of natural variation (mole fraction) 

excitation energy  
^{217}U  92  125  217.02437(9)  26(14) ms [16(+216) ms]  1/2#  
^{218}U  92  126  218.02354(3)  6(5) ms  0+  
^{219}U  92  127  219.02492(6)  55(25) µs [42(+3413) µs]  9/2+#  
^{220}U  92  128  220.02472(22)#  60# ns  0+  
^{221}U  92  129  221.02640(11)#  700# ns  9/2+#  
^{222}U  92  130  222.02609(11)#  1.4(7) µs [1.0(+104) µs]  0+  
^{223}U  92  131  223.02774(8)  21(8) µs [18(+105) µs]  7/2+#  
^{224}U  92  132  224.027605(27)  940(270) µs  0+  
^{225}U  92  133  225.02939#  61(4) ms  (5/2+)#  
^{226}U  92  134  226.029339(14)  269(6) ms  0+  
^{227}U  92  135  227.031156(18)  1.1(1) min  (3/2+)  
^{228}U  92  136  228.031374(16)  9.1(2) min  0+  
^{229}U  92  137  229.033506(6)  58(3) min  (3/2+)  
^{230}U  92  138  230.033940(5)  20.8 d  0+  
^{231}U  92  139  231.036294(3)  4.2(1) d  (5/2)(+#)  
^{232}U  92  140  232.0371562(24)  68.9(4) y  0+  
^{233}U  92  141  233.0396352(29)  1.592(2)×10^{5} y  5/2+  
^{234}U  92  142  234.0409521(20)  2.455(6)×10^{5} y  0+  [0.000054(5)]  0.0000500.000059 
^{234m}U  1421.32(10) keV  33.5(20) µs  6  
^{235}U  92  143  235.0439299(20)  7.04(1)×10^{8} y  7/2  [0.007204(6)]  0.0071980.007207 
^{235m}U  0.0765(4) keV  ~26 min  1/2+  
^{236}U  92  144  236.045568(2)  2.342(3)×10^{7} y  0+  
^{236m1}U  1052.89(19) keV  100(4) ns  (4)  
^{236m2}U  2750(10) keV  120(2) ns  (0+)  
^{237}U  92  145  237.0487302(20)  6.75(1) d  1/2+  
^{238}U  92  146  238.0507882(20)  4.468(3)×10^{9} y  0+  [0.992742(10)]  0.9927390.992752 
^{238m}U  2557.9(5) keV  280(6) ns  0+  
^{239}U  92  147  239.0542933(21)  23.45(2) min  5/2+  
^{239m1}U  20(20)# keV  >250 ns  (5/2+)  
^{239m2}U  133.7990(10) keV  780(40) ns  1/2+  
^{240}U  92  148  240.056592(6)  14.1(1) h  0+  
^{241}U  92  149  241.06033(32)#  5# min  7/2+#  
^{242}U  92  150  242.06293(22)#  16.8(5) min  0+ 
Isotopes of protactinium  Isotopes of uranium  Isotopes of neptunium 
Index to isotope pages · Table of nuclides 
Redirecting to Isotopes of uranium
