Isotopes of radium

Radium (88Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given. The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1600 years. 226Ra occurs in the decay chain of 238U (often referred to as the radium series). Radium has 34 known isotopes from 201Ra to 234Ra.

Isotopes of radium (88Ra)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
223Ra trace 11.43 d α 219Rn
224Ra trace 3.6319 d α 220Rn
225Ra trace 14.9 d β− 225Ac
226Ra trace 1599 y α 222Rn
228Ra trace 5.75 y β− 228Ac

In 2013 it was discovered that the nucleus of radium-224 is pear-shaped.[2] This was the first discovery of an asymmetrical nucleus.

List of isotopes
Nuclide
[n 1]		 Historic
name		 Z N Isotopic mass (Da)
[n 2][n 3]		 Half-life
 Decay
mode
[n 4]		 Daughter
isotope
[n 5]		 Spin and
parity
[n 6][n 7]		 Isotopic
abundance
Excitation energy[n 7]
201Ra[3] 88 113 8+40
−4 ms		 α 197Rn (3/2−)
201mRa[4] 260(30) keV 1.6+7.7
−0.7 ms		 α 197mRn (13/2+)
202Ra 88 114 202.00989(7) 3.8+1.3
−0.8 ms[3]		 α 198Rn 0+
203Ra 88 115 203.00927(9) 4(3) ms α 199Rn (3/2−)
β+ (rare) 203Fr
203mRa 220(90) keV 41(17) ms α 199Rn (13/2+)
β+ (rare) 203Fr
204Ra 88 116 204.006500(17) 60(11) ms
[59(+12−9) ms]		 α (99.7%) 200Rn 0+
β+ (.3%) 204Fr
205Ra 88 117 205.00627(9) 220(40) ms
[210(+60−40) ms]		 α 201Rn (3/2−)
β+ (rare) 205Fr
205mRa 310(110)# keV 180(50) ms
[170(+60−40) ms]		 α 201Rn (13/2+)
IT (rare) 205Ra
206Ra 88 118 206.003827(19) 0.24(2) s α 202Rn 0+
207Ra 88 119 207.00380(6) 1.3(2) s α (90%) 203Rn (5/2−, 3/2−)
β+ (10%) 207Fr
207mRa 560(50) keV 57(8) ms IT (85%) 207Ra (13/2+)
α (15%) 203Rn
β+ (.55%) 207Fr
208Ra 88 120 208.001840(17) 1.3(2) s α (95%) 204Rn 0+
β+ (5%) 208Fr
208mRa 1800(200) keV 270 ns (8+)
209Ra 88 121 209.00199(5) 4.6(2) s α (90%) 205Rn 5/2−
β+ (10%) 209Fr
210Ra 88 122 210.000495(16) 3.7(2) s α (96%) 206Rn 0+
β+ (4%) 210Fr
210mRa 1800(200) keV 2.24 μs (8+)
211Ra 88 123 211.000898(28) 13(2) s α (97%) 207Rn 5/2(−)
β+ (3%) 211Fr
212Ra 88 124 211.999794(12) 13.0(2) s α (85%) 208Rn 0+
β+ (15%) 212Fr
212m1Ra 1958.4(5) keV 10.9(4) μs (8)+
212m2Ra 2613.4(5) keV 0.85(13) μs (11)−
213Ra 88 125 213.000384(22) 2.74(6) min α (80%) 209Rn 1/2−
β+ (20%) 213Fr
213mRa 1769(6) keV 2.1(1) ms IT (99%) 213Ra 17/2−#
α (1%) 209Rn
214Ra 88 126 214.000108(10) 2.46(3) s α (99.94%) 210Rn 0+
β+ (.06%) 214Fr
215Ra 88 127 215.002720(8) 1.55(7) ms α 211Rn (9/2+)#
215m1Ra 1877.8(5) keV 7.1(2) μs (25/2+)
215m2Ra 2246.9(5) keV 1.39(7) μs (29/2−)
215m3Ra 3756.6(6)+X keV 0.555(10) μs (43/2−)
216Ra 88 128 216.003533(9) 182(10) ns α 212Rn 0+
EC (<1×10−8%) 216Fr
217Ra 88 129 217.006320(9) 1.63(17) μs α 213Rn (9/2+)
218Ra 88 130 218.007140(12) 25.2(3) μs α 214Rn 0+
219Ra 88 131 219.010085(9) 10(3) ms α 215Rn (7/2)+
220Ra 88 132 220.011028(10) 17.9(14) ms α 216Rn 0+
221Ra 88 133 221.013917(5) 28(2) s α 217Rn 5/2+ Trace[n 8]
CD (1.2×10−10%)[n 9] 207Pb
14C
222Ra 88 134 222.015375(5) 38.0(5) s α 218Rn 0+
CD (3×10−8%) 208Pb
14C
223Ra[n 10] Actinium X 88 135 223.0185022(27) 11.43(5) d α 219Rn 3/2+ Trace[n 11]
CD (6.4×10−8%) 209Pb
14C
224Ra Thorium X 88 136 224.0202118(24) 3.6319(23) d α 220Rn 0+ Trace[n 12]
CD (4.3×10−9%) 210Pb
14C
225Ra 88 137 225.023612(3) 14.9(2) d β− 225Ac 1/2+ Trace[n 13]
α (2.0×10−3%)[5] 221Rn
226Ra Radium[n 14] 88 138 226.0254098(25) 1600(7) y α[n 15] 222Rn 0+ Trace[n 16]
CD (2.6×10−9%) 212Pb
14C
227Ra 88 139 227.0291778(25) 42.2(5) min β− 227Ac 3/2+
228Ra Mesothorium 1 88 140 228.0310703(26) 5.75(3) y β− 228Ac 0+ Trace[n 12]
229Ra 88 141 229.034958(20) 4.0(2) min β− 229Ac 5/2(+)
230Ra 88 142 230.037056(13) 93(2) min β− 230Ac 0+
231Ra 88 143 231.04122(32)# 103(3) s β− 231Ac (5/2+)
231mRa 66.21(9) keV ~53 μs (1/2+)
232Ra 88 144 232.04364(30)# 250(50) s β− 232Ac 0+
233Ra 88 145 233.04806(50)# 30(5) s β− 233Ac 1/2+#
234Ra 88 146 234.05070(53)# 30(10) s β− 234Ac 0+
This table header & footer:
  1. mRa – Excited nuclear isomer.
  2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. Modes of decay:
    CD:Cluster decay
    EC:Electron capture
    IT:Isomeric transition
  5. Bold symbol as daughter – Daughter product is stable.
  6. ( ) spin value – Indicates spin with weak assignment arguments.
  7. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  8. Intermediate decay product of 237Np
  9. Lightest known nuclide to undergo cluster decay
  10. Used for treating bone cancer
  11. Intermediate decay product of 235U
  12. Intermediate decay product of 232Th
  13. Intermediate decay product of 237Np
  14. Source of element's name
  15. Theoretically capable of β-β- decay to 226Th[1]
  16. Intermediate decay product of 238U

Actinides vs fission products
Actinides and fission products by half-life
Actinides[6] by decay chain Half-life
range (a)		 Fission products of 235U by yield[7]
4n 4n + 1 4n + 2 4n + 3 4.5–7% 0.04–1.25% <0.001%
228Ra№ 4–6 a 155Euþ
244Cmƒ 241Puƒ 250Cf 227Ac№ 10–29 a 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ 243Cmƒ 29–97 a 137Cs 151Smþ 121mSn
248Bk[8] 249Cfƒ 242mAmƒ 141–351 a

No fission products have a half-life
in the range of 100 a–210 ka ...

241Amƒ 251Cfƒ[9] 430–900 a
226Ra№ 247Bk 1.3–1.6 ka
240Pu 229Th 246Cmƒ 243Amƒ 4.7–7.4 ka
245Cmƒ 250Cm 8.3–8.5 ka
239Puƒ 24.1 ka
230Th№ 231Pa№ 32–76 ka
236Npƒ 233Uƒ 234U№ 150–250 ka 99Tc₡ 126Sn
248Cm 242Pu 327–375 ka 79Se₡
1.53 Ma 93Zr
237Npƒ 2.1–6.5 Ma 135Cs₡ 107Pd
236U 247Cmƒ 15–24 Ma 129I₡
244Pu 80 Ma

... nor beyond 15.7 Ma[10]

232Th№ 238U№ 235Uƒ№ 0.7–14.1 Ga
  • ₡,  has thermal neutron capture cross section in the range of 8–50 barns
  • ƒ,  fissile
  • №,  primarily a naturally occurring radioactive material (NORM)
  • þ,  neutron poison (thermal neutron capture cross section greater than 3k barns)

References
  1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. "First observations of short-lived pear-shaped atomic nuclei". 28 November 2023.
  3. Kalaninová, Z.; Antalic, S.; Andreyev, A. N.; Heßberger, F. P.; Ackermann, D.; Andel, B.; Bianco, L.; Hofmann, S.; Huyse, M.; Kindler, B.; Lommel, B.; Mann, R.; Page, R. D.; Sapple, P. J.; Thomson, J.; Van Duppen, P.; Venhart, M. (12 May 2014). "Decay of 201–203Ra and 200–202Fr" (PDF). Physical Review C. 89 (5): 054312. Bibcode:2014PhRvC..89e4312K. doi:10.1103/PhysRevC.89.054312. ISSN 0556-2813. Retrieved 11 June 2023.
  4. Uusitalo, J.; Leino, M.; Enqvist, T.; Eskola, K.; Grahn, T.; Greenlees, P. T.; Jones, P.; Julin, R.; Juutinen, S.; Keenan, A.; Kettunen, H.; Koivisto, H.; Kuusiniemi, P.; Leppänen, A.-P.; Nieminen, P.; Pakarinen, J.; Rahkila, P.; Scholey, C. (11 February 2005). "α decay studies of very neutron-deficient francium and radium isotopes". Physical Review C. 71 (2): 024306. Bibcode:2005PhRvC..71b4306U. doi:10.1103/PhysRevC.71.024306. ISSN 0556-2813.
  5. Liang, C. F.; Paris, P.; Sheline, R. K. (2000-09-19). "α decay of 225Ra". Physical Review C. 62 (4). American Physical Society (APS): 047303. Bibcode:2000PhRvC..62d7303L. doi:10.1103/physrevc.62.047303. ISSN 0556-2813.
  6. Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
  7. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
  8. Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
    "The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 [years]. No growth of Cf248 was detected, and a lower limit for the β− half-life can be set at about 104 [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
  9. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
  10. Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is eight quadrillion years.
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