Isotopes of radium

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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 1600 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)[1][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 Actinium X 88 135 223.0185022(27) 11.43(5) d α 219Rn 3/2+ Trace[n 4]
CD (6.4×10−8%) 209Pb
14C
224Ra Thorium X 88 136 224.0202118(24) 3.6319(23) d α 220Rn 0+ Trace[n 5]
CD (4.3×10−9%) 210Pb
14C
225Ra 88 137 225.023612(3) 14.9(2) d β- 225Ac 1/2+
226Ra Radium[n 6] 88 138 226.0254098(25) 1600(7) y α 222Rn 0+ Trace[n 7]
β-β- (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 5]
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. ^ Intermediate decay product of 235U
  5. ^ a b Intermediate decay product of 232Th
  6. ^ Source of element's name
  7. ^ 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. ^ http://www.nucleonica.net/unc.aspx


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