Isotopes of radium

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

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

241Amƒ 251Cfƒ[4] 430–900
226Ra 247Bk 1.3 k – 1.6 k
240Puƒ№ 229Th 246Cmƒ 243Amƒ 4.7 k – 7.4 k
245Cmƒ 250Cm 8.3 k – 8.5 k
239Puƒ№ 24.1 k
230Th 231Pa 32 k – 76 k
236Npƒ 233Uƒ№ 234U 150 k – 250 k 99Tc 126Sn
248Cm 242Puƒ 327 k – 375 k 79Se
1.53 M 93Zr
237Npƒ№ 2.1 M – 6.5 M 135Cs 107Pd
236U 247Cmƒ 15 M – 24 M 129I
244Pu 80 M

... nor beyond 15.7 M years[5]

232Th 238U 235Uƒ№ 0.7 G – 14.1 G

Legend for superscript symbols
₡  has thermal neutron capture cross section in the range of 8–50 barns
ƒ  fissile
metastable isomer
№  naturally occurring radioactive material (NORM)
þ  neutron poison (thermal neutron capture cross section greater than 3k barns)
†  range 4–97 y: Medium-lived fission product
‡  over 200,000 y: Long-lived fission product

Radium (Ra) has no stable or nearly stable isotopes, and thus a standard atomic mass cannot be given. The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1,600 years. 226Ra occurs in the decay chain of 238U (often referred to as the radium series.) Radium has 33 known isotopes from 202Ra to 234Ra.

Table[edit]

nuclide
symbol
historic
name
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[6][n 1]
daughter
isotope(s)[n 2]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
202Ra 88 114 202.00989(7) 2.6(21) ms
[0.7(+33−3) ms]
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+
β+β+ (rare) 218Rn
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+
CD (1.2×10−10%) 207Pb
14C
222Ra 88 134 222.015375(5) 38.0(5) s α 218Rn 0+ Trace[n 3]
CD (3×10−8%) 208Pb
14C
223Ra[n 4] Actinium X 88 135 223.0185022(27) 11.43(5) d α 219Rn 3/2+ Trace[n 5]
CD (6.4×10−8%) 209Pb
14C
224Ra Thorium X 88 136 224.0202118(24) 3.6319(23) d α 220Rn 0+ Trace[n 6]
CD (4.3×10−9%) 210Pb
14C
225Ra 88 137 225.023612(3) 14.9(2) d β 225Ac 1/2+
226Ra Radium[n 7] 88 138 226.0254098(25) 1600(7) y α 222Rn 0+ [n 8]
ββ (rare) 226Th
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 6]
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+
  1. ^ Abbreviations:
    CD: Cluster decay
    EC: Electron capture
    IT: Isomeric transition
  2. ^ Bold for stable isotopes
  3. ^ Intermediate decay product of 238U
  4. ^ Used for treating bone cancer
  5. ^ Intermediate decay product of 235U
  6. ^ a b Intermediate decay product of 232Th
  7. ^ Source of element's name
  8. ^ Intermediate decay product of 238U

Notes[edit]

  • 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.

References[edit]

  1. ^ 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 isotopes have half-lives of at least four years (the longest-lived isotope 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.
  2. ^ Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
  3. ^ 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. 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 y. No growth of Cf248 was detected, and a lower limit for the β half-life can be set at about 104 y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y."
  4. ^ This is the heaviest isotope with a half-life of at least four years before the "Sea of Instability".
  5. ^ Excluding those "classically stable" isotopes with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is nearly eight quadrillion years.
  6. ^ "Universal Nuclide Chart". nucleonica. (registration required (help)). 


Isotopes of francium Isotopes of radium Isotopes of actinium
Table of nuclides