Isotopes of radium
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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, which is in the decay chain of 238U (the uranium or radium series).
Radium now has 34 known isotopes from 201Ra to 234Ra.
In the early history of the study of radioactivity, the different natural isotopes of radium were given different names (as were those of other radioactive elements), as it was not until Frederick Soddy's scientific work in the 1900s and 1910s that the concept of isotopes was employed. In this scheme, 223Ra was named actinium X (AcX), 224Ra thorium X (ThX), 226Ra radium (Ra), and 228Ra mesothorium 1 (MsTh1). When it was realized that all of these are isotopes of the same element, many of these names fell out of use, and "radium" came to refer to all isotopes, not just 226Ra, though mesothorium 1 in particular was still used for some time, with a footnote explaining that it referred to 228Ra. The known decay products of radium-226 received historical names including "radium", starting with radium emanation and then ranging from radium A to radium G, with the letter indicating approximately how far they were down the chain from their parent.
In 2013 it was discovered that the nucleus of radium-224 is pear-shaped. This was the first discovery of an asymmetrical nucleus.
List of isotopes
| Nuclide | Historic name | Z | N | Isotopic mass (Da) | Discovery year | Half-life | Decay mode | Daughter isotope | Spin and parity | Isotopic abundance |
|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy | ||||||||||
| 201Ra | 88 | 113 | 201.012815(22) | 20(30) ms | α | 197Rn | (3/2−) | |||
| 201mRa | 263(26) keV | 6(5) ms | α | 197Rn | 13/2+ | |||||
| 202Ra | 88 | 114 | 202.009742(16) | 4.1(11) ms | α | 198Rn | 0+ | |||
| 203Ra | 88 | 115 | 203.009234(10) | 36(13) ms | α | 199Rn | 3/2− | |||
| 203mRa | 246(14) keV | 25(5) ms | α | 199Rn | 13/2+ | |||||
| 204Ra | 88 | 116 | 204.0065069(96) | 60(9) ms | α | 200Rn | 0+ | |||
| 205Ra | 88 | 117 | 205.006231(24) | 220(50) ms | α | 201Rn | 3/2− | |||
| 205mRa | 263(25) keV | 180(50) ms | α | 201Rn | 13/2+ | |||||
| 206Ra | 88 | 118 | 206.003828(19) | 0.24(2) s | α | 202Rn | 0+ | |||
| 207Ra | 88 | 119 | 207.003772(63) | 1.38(18) s | α (86%) | 203Rn | 5/2−# | |||
| β+ (14%) | 207Fr | |||||||||
| 207mRa | 560(60) keV | 57(8) ms | IT (85%#) | 207Ra | 13/2+ | |||||
| α (?%) | 203mRn | |||||||||
| β+ ? | 207Fr | |||||||||
| 208Ra | 88 | 120 | 208.0018550(97) | 1.110(45) s | α (87%) | 204Rn | 0+ | |||
| β+ (13%) | 208Fr | |||||||||
| 208mRa | 2147.4(4) keV | 263(17) ns | IT | 208Ra | (8+) | |||||
| 209Ra | 88 | 121 | 209.0019949(62) | 4.71(8) s | α (90%) | 205Rn | 5/2− | |||
| 209mRa | 882.4(7) keV | 117(5) μs | α (90%) | 205Rn | 13/2+ | |||||
| β+ (10%) | 209Fr | |||||||||
| 210Ra | 88 | 122 | 210.0004754(99) | 4.0(1) s | α | 206Rn | 0+ | |||
| 210mRa | 2050.9(7) keV | 2.29(3) μs | IT | 210Ra | 8+ | |||||
| 211Ra | 88 | 123 | 211.0008930(53) | 12.6(12) s | α | 207Rn | 5/2− | |||
| 211mRa | 1198.1(8) keV | 9.5(3) μs | IT | 211Ra | 13/2+ | |||||
| 212Ra | 88 | 124 | 211.999787(11) | 13.0(2) s | α | 208Rn | 0+ | |||
| β+ ? | 212Fr | |||||||||
| 212m1Ra | 1958.4(20) keV | 9.3(9) μs | IT | 212Ra | 8+ | |||||
| 212m2Ra | 2613.3(20) keV | 0.85(13) μs | IT | 212Ra | 11− | |||||
| 213Ra | 88 | 125 | 213.000371(11) | 2.73(5) min | α (87%) | 209Rn | 1/2− | |||
| β+ (13%) | 213Fr | |||||||||
| 213mRa | 1768(4) keV | 2.20(5) ms | IT (99.4%) | 213Ra | (17/2−) | |||||
| α (0.6%) | 209Rn | |||||||||
| 214Ra | 88 | 126 | 214.0000996(56) | 2.437(16) s | α (99.941%) | 210Rn | 0+ | |||
| β+ (0.059%) | 214Fr | |||||||||
| 214m1Ra | 1819.7(18) keV | 118(7) ns | IT | 214Ra | 6+ | |||||
| 214m2Ra | 1865.2(18) keV | 67.3(15) μs | IT (99.91%) | 214Ra | 8+ | |||||
| α (0.09%) | 210Rn | |||||||||
| 214m3Ra | 2683.2(18) keV | 295(7) ns | IT | 214Ra | 11− | |||||
| 214m4Ra | 3478.4(18) keV | 279(4) ns | IT | 214Ra | 14+ | |||||
| 214m5Ra | 4146.8(18) keV | 225(4) ns | IT | 214Ra | 17− | |||||
| 214m6Ra | 6577.0(18) keV | 128(4) ns | IT | 214Ra | (25−) | |||||
| 215Ra | 88 | 127 | 215.0027182(77) | 1.669(9) ms | α | 211Rn | 9/2+# | |||
| 215m1Ra | 1877.8(3) keV | 7.31(13) μs | IT | 215Ra | (25/2+) | |||||
| 215m2Ra | 2246.9(4) keV | 1.39(7) μs | IT | 215Ra | (29/2−) | |||||
| 215m3Ra | 3807(50)# keV | 555(10) ns | IT | 215Ra | (43/2−) | |||||
| 216Ra | 88 | 128 | 216.0035335(86) | 172(7) ns | α | 212Rn | 0+ | |||
| EC (<1×10−8%) | 216Fr | |||||||||
| 217Ra | 88 | 129 | 217.0063227(76) | 1.95(12) μs | α | 213Rn | (9/2+) | |||
| 218Ra | 88 | 130 | 218.007134(11) | 25.91(14) μs | α | 214Rn | 0+ | |||
| 219Ra | 88 | 131 | 219.0100847(73) | 9(2) ms | α | 215Rn | (7/2)+ | |||
| 219mRa | 16.7(8) keV | 10(3) ms | α | 215Rn | (11/2)+ | |||||
| 220Ra | 88 | 132 | 220.0110275(82) | 18.1(12) ms | α | 216Rn | 0+ | |||
| 221Ra | 88 | 133 | 221.0139173(05) | 25(4) s | α | 217Rn | 5/2+ | Trace | ||
| CD (1.2×10−10%) | 207Pb 14C | |||||||||
| 222Ra | 88 | 134 | 222.0153734(48) | 33.6(4) s | α | 218Rn | 0+ | |||
| CD (3.0×10−8%) | 208Pb 14C | |||||||||
| 223Ra | Actinium X | 88 | 135 | 223.0185006(22) | 11.4352(10) d | α | 219Rn | 3/2+ | Trace | |
| CD (8.9×10−8%) | 209Pb 14C | |||||||||
| 224Ra | Thorium X | 88 | 136 | 224.0202104(19) | 3.6316(14) d | α | 220Rn | 0+ | Trace | |
| CD (4.0×10−9%) | 210Pb 14C | |||||||||
| 225Ra | 88 | 137 | 225.0236105(28) | 14.82(19) d | β− | 225Ac | 1/2+ | Trace | ||
| α (0.0026%) | 221Rn | |||||||||
| 226Ra | Radium | 88 | 138 | 226.0254082(21) | 1600(7) y | α | 222Rn | 0+ | Trace | |
| CD (2.6×10−9%) | 212Pb 14C | |||||||||
| 227Ra | 88 | 139 | 227.0291762(21) | 42.2(5) min | β− | 227Ac | 3/2+ | |||
| 228Ra | Mesothorium 1 | 88 | 140 | 228.0310686(21) | 5.75(3) y | β− | 228Ac | 0+ | Trace | |
| 229Ra | 88 | 141 | 229.034957(17) | 4.0(2) min | β− | 229Ac | 5/2+ | |||
| 230Ra | 88 | 142 | 230.037055(11) | 93(2) min | β− | 230Ac | 0+ | |||
| 231Ra | 88 | 143 | 231.041027(12) | 104(1) s | β− | 231Ac | (5/2+) | |||
| 231mRa | 66.21(9) keV | ~53 μs | IT | 231Ra | (1/2+) | |||||
| 232Ra | 88 | 144 | 232.0434753(98) | 4.0(3) min | β− | 232Ac | 0+ | |||
| 233Ra | 88 | 145 | 233.0475946(92) | 30(5) s | β− | 233Ac | 1/2+# | |||
| 234Ra | 88 | 146 | 234.0503821(90) | 30(10) s | β− | 234Ac | 0+ | |||
| This table header & footer: view |
Actinides vs fission products
| Actinides and fission products by half-life vte | |||||||
|---|---|---|---|---|---|---|---|
| Actinides by decay chain | Half-life range (a) | Fission products of 235U by yield | |||||
| 4n (Thorium) | 4n + 1 (Neptunium) | 4n + 2 (Radium) | 4n + 3 (Actinium) | 4.5–7% | 0.04–1.25% | <0.001% | |
| 228Ra№ | 4–6 a | 155Euþ | |||||
| 248Bk | > 9 a | ||||||
| 244Cmƒ | 241Puƒ | 250Cf | 227Ac№ | 10–29 a | 90Sr | 85Kr | 113mCdþ |
| 232Uƒ | 238Puƒ | 243Cmƒ | 29–97 a | 137Cs | 151Smþ | 121mSn | |
| 249Cfƒ | 242mAmƒ | 141–351 a | No fission products have a half-life in the range of 100 a–210 ka ... | ||||
| 241Amƒ | 251Cfƒ | 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₡ | ||||
| 1.33 Ma | 135Cs₡ | ||||||
| 237Npƒ | 1.61–6.5 Ma | 93Zr | 107Pd | ||||
| 236U | 247Cmƒ | 15–24 Ma | 129I₡ | ||||
| 244Pu | 80 Ma | ... nor beyond 15.7 Ma | |||||
| 232Th№ | 238U№ | 235Uƒ№ | 0.7–14.1 Ga | ||||
| ₡, has thermal neutron capture cross section in the range of 8–50 barnsƒ, fissile№, primarily a naturally occurring radioactive material (NORM)þ, neutron poison (thermal neutron capture cross section greater than 3k barns) |
- Isotope masses from: Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), , Nuclear Physics A, 729: 3–128, Bibcode:, doi:
- Half-life, spin, and isomer data selected from the following sources. Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), , Nuclear Physics A, 729: 3–128, Bibcode:, doi: National Nuclear Data Center. . Brookhaven National Laboratory. Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.