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 , 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, Ra was named actinium X (AcX), Ra thorium X (ThX), Ra radium (Ra), and Ra mesothorium 1 (MsTh). 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 Ra, though mesothorium 1 in particular was still used for some time, with a footnote explaining that it referred to Ra. 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

|-id=Radium-201 | ²⁰¹Ra | | style="text-align:right" | 88 | style="text-align:right" | 113 | 201.012815(22) | 20(30)&nbsp;ms | α | ¹⁹⁷Rn | (3/2−) | |-id=Radium-201m | style="text-indent:1em" | ^201mRa | | colspan="3" style="text-indent:2em" | 263(26)&nbsp;keV | 6(5)&nbsp;ms | α | ¹⁹⁷Rn | 13/2+ | |-id=Radium-202 | ²⁰²Ra | | style="text-align:right" | 88 | style="text-align:right" | 114 | 202.009742(16) | 4.1(11)&nbsp;ms | α | ¹⁹⁸Rn | 0+ | |-id=Radium-203 | ²⁰³Ra | | style="text-align:right" | 88 | style="text-align:right" | 115 | 203.009234(10) | 36(13)&nbsp;ms | α | ¹⁹⁹Rn | 3/2− | |-id=Radium-203m | style="text-indent:1em" | ^203mRa | | colspan="3" style="text-indent:2em" | 246(14)&nbsp;keV | 25(5)&nbsp;ms | α | ¹⁹⁹Rn | 13/2+ | |-id=Radium-204 | ²⁰⁴Ra | | style="text-align:right" | 88 | style="text-align:right" | 116 | 204.0065069(96) | 60(9)&nbsp;ms | α | ²⁰⁰Rn | 0+ | |-id=Radium-205 | ²⁰⁵Ra | | style="text-align:right" | 88 | style="text-align:right" | 117 | 205.006231(24) | 220(50)&nbsp;ms | α | ²⁰¹Rn | 3/2− | |-id=Radium-205m | style="text-indent:1em" | ^205mRa | | colspan="3" style="text-indent:2em" | 263(25)&nbsp;keV | 180(50)&nbsp;ms | α | ²⁰¹Rn | 13/2+ | |-id=Radium-206 | ²⁰⁶Ra | | style="text-align:right" | 88 | style="text-align:right" | 118 | 206.003828(19) | 0.24(2)&nbsp;s | α | ²⁰²Rn | 0+ | |-id=Radium-207 | rowspan=2|²⁰⁷Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 119 | rowspan=2|207.003772(63) | rowspan=2|1.38(18)&nbsp;s | α (86%) | ²⁰³Rn | rowspan=2|5/2−# | rowspan=2| |- | β⁺ (14%) | ²⁰⁷Fr |-id=Radium-207m | rowspan=3 style="text-indent:1em" | ^207mRa | rowspan=3| | rowspan=3 colspan="3" style="text-indent:2em" | 560(60)&nbsp;keV | rowspan=3|57(8)&nbsp;ms | IT (85%#) | ²⁰⁷Ra | rowspan=3|13/2+ | rowspan=3| |- | α (?%) | ^203mRn |- | β⁺ ? | ²⁰⁷Fr |-id=Radium-208 | rowspan=2|²⁰⁸Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 120 | rowspan=2|208.0018550(97) | rowspan=2|1.110(45)&nbsp;s | α (87%) | ²⁰⁴Rn | rowspan=2|0+ | rowspan=2| |- | β⁺ (13%) | ²⁰⁸Fr |-id=Radium-208m | style="text-indent:1em" | ^208mRa | | colspan="3" style="text-indent:2em" | 2147.4(4)&nbsp;keV | 263(17)&nbsp;ns | IT | ²⁰⁸Ra | (8+) | |-id=Radium-209 | ²⁰⁹Ra | | style="text-align:right" | 88 | style="text-align:right" | 121 | 209.0019949(62) | 4.71(8)&nbsp;s | α (90%) | ²⁰⁵Rn | 5/2− | |-id=Radium-209m | rowspan=2 style="text-indent:1em" | ^209mRa | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 882.4(7)&nbsp;keV | rowspan=2|117(5)&nbsp;μs | α (90%) | ²⁰⁵Rn | rowspan=2|13/2+ | rowspan=2| |- | β⁺ (10%) | ²⁰⁹Fr |-id=Radium-210 | ²¹⁰Ra | | style="text-align:right" | 88 | style="text-align:right" | 122 | 210.0004754(99) | 4.0(1)&nbsp;s | α | ²⁰⁶Rn | 0+ | |-id=Radium-210m | style="text-indent:1em" | ^210mRa | | colspan="3" style="text-indent:2em" | 2050.9(7)&nbsp;keV | 2.29(3)&nbsp;μs | IT | ²¹⁰Ra | 8+ | |-id=Radium-211 | ²¹¹Ra | | style="text-align:right" | 88 | style="text-align:right" | 123 | 211.0008930(53) | 12.6(12)&nbsp;s | α | ²⁰⁷Rn | 5/2− | |-id=Radium-211m | style="text-indent:1em" | ^211mRa | | colspan="3" style="text-indent:2em" | 1198.1(8)&nbsp;keV | 9.5(3)&nbsp;μs | IT | ²¹¹Ra | 13/2+ | |-id=Radium-212 | rowspan=2|²¹²Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 124 | rowspan=2|211.999787(11) | rowspan=2|13.0(2)&nbsp;s | α | ²⁰⁸Rn | rowspan=2|0+ | rowspan=2| |- | β⁺ ? | ²¹²Fr |-id=Radium-212m1 | style="text-indent:1em" | ^212m1Ra | | colspan="3" style="text-indent:2em" | 1958.4(20)&nbsp;keV | 9.3(9)&nbsp;μs | IT | ²¹²Ra | 8+ | |-id=Radium-212m2 | style="text-indent:1em" | ^212m2Ra | | colspan="3" style="text-indent:2em" | 2613.3(20)&nbsp;keV | 0.85(13)&nbsp;μs | IT | ²¹²Ra | 11− | |-id=Radium-213 | rowspan=2|²¹³Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 125 | rowspan=2|213.000371(11) | rowspan=2|2.73(5)&nbsp;min | α (87%) | ²⁰⁹Rn | rowspan=2|1/2− | rowspan=2| |- | β⁺ (13%) | ²¹³Fr |-id=Radium-213m | rowspan=2 style="text-indent:1em" | ^213mRa | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 1768(4)&nbsp;keV | rowspan=2|2.20(5)&nbsp;ms | IT (99.4%) | ²¹³Ra | rowspan=2|(17/2−) | rowspan=2| |- | α (0.6%) | ²⁰⁹Rn |-id=Radium-214 | rowspan=2|²¹⁴Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 126 | rowspan=2|214.0000996(56) | rowspan=2|2.437(16)&nbsp;s | α (99.941%) | ²¹⁰Rn | rowspan=2|0+ | rowspan=2| |- | β⁺ (0.059%) | ²¹⁴Fr |-id=Radium-214m1 | style="text-indent:1em" | ^214m1Ra | | colspan="3" style="text-indent:2em" | 1819.7(18)&nbsp;keV | 118(7)&nbsp;ns | IT | ²¹⁴Ra | 6+ | |-id=Radium-214m2 | rowspan=2 style="text-indent:1em" | ^214m2Ra | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 1865.2(18)&nbsp;keV | rowspan=2|67.3(15)&nbsp;μs | IT (99.91%) | ²¹⁴Ra | rowspan=2|8+ | rowspan=2| |- | α (0.09%) | ²¹⁰Rn |-id=Radium-214m3 | style="text-indent:1em" | ^214m3Ra | | colspan="3" style="text-indent:2em" | 2683.2(18)&nbsp;keV | 295(7)&nbsp;ns | IT | ²¹⁴Ra | 11− | |-id=Radium-214m4 | style="text-indent:1em" | ^214m4Ra | | colspan="3" style="text-indent:2em" | 3478.4(18)&nbsp;keV | 279(4)&nbsp;ns | IT | ²¹⁴Ra | 14+ | |-id=Radium-214m5 | style="text-indent:1em" | ^214m5Ra | | colspan="3" style="text-indent:2em" | 4146.8(18)&nbsp;keV | 225(4)&nbsp;ns | IT | ²¹⁴Ra | 17− | |-id=Radium-214m6 | style="text-indent:1em" | ^214m6Ra | | colspan="3" style="text-indent:2em" | 6577.0(18)&nbsp;keV | 128(4)&nbsp;ns | IT | ²¹⁴Ra | (25−) | |-id=Radium-215 | ²¹⁵Ra | | style="text-align:right" | 88 | style="text-align:right" | 127 | 215.0027182(77) | 1.669(9)&nbsp;ms | α | ²¹¹Rn | 9/2+# | |-id=Radium-215m1 | style="text-indent:1em" | ^215m1Ra | | colspan="3" style="text-indent:2em" | 1877.8(3)&nbsp;keV | 7.31(13)&nbsp;μs | IT | ²¹⁵Ra | (25/2+) | |-id=Radium-215m2 | style="text-indent:1em" | ^215m2Ra | | colspan="3" style="text-indent:2em" | 2246.9(4)&nbsp;keV | 1.39(7)&nbsp;μs | IT | ²¹⁵Ra | (29/2−) | |-id=Radium-215m3 | style="text-indent:1em" | ^215m3Ra | | colspan="3" style="text-indent:2em" | 3807(50)#&nbsp;keV | 555(10)&nbsp;ns | IT | ²¹⁵Ra | (43/2−) | |-id=Radium-216 | rowspan=2|²¹⁶Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 128 | rowspan=2|216.0035335(86) | rowspan=2|172(7)&nbsp;ns | α | ²¹²Rn | rowspan=2|0+ | rowspan=2| |- | EC (<1×10^{−8}%) | ²¹⁶Fr |-id=Radium-217 | ²¹⁷Ra | | style="text-align:right" | 88 | style="text-align:right" | 129 | 217.0063227(76) | 1.95(12)&nbsp;μs | α | ²¹³Rn | (9/2+) | |-id=Radium-218 |²¹⁸Ra | | style="text-align:right" | 88 | style="text-align:right" | 130 | 218.007134(11) | 25.91(14)&nbsp;μs | α | ²¹⁴Rn | 0+ | |-id=Radium-219 | ²¹⁹Ra | | style="text-align:right" | 88 | style="text-align:right" | 131 | 219.0100847(73) | 9(2)&nbsp;ms | α | ²¹⁵Rn | (7/2)+ | |-id=Radium-219m | style="text-indent:1em" | ^219mRa | | colspan="3" style="text-indent:2em" | 16.7(8)&nbsp;keV | 10(3)&nbsp;ms | α | ²¹⁵Rn | (11/2)+ | |-id=Radium-220 | ²²⁰Ra | | style="text-align:right" | 88 | style="text-align:right" | 132 | 220.0110275(82) | 18.1(12)&nbsp;ms | α | ²¹⁶Rn | 0+ | |-id=Radium-221 | rowspan=2|²²¹Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 133 | rowspan=2|221.0139173(05) | rowspan=2|25(4)&nbsp;s | α | ²¹⁷Rn | rowspan=2|5/2+ | rowspan=2|Trace |- | CD (1.2×10^{−10}%) | ²⁰⁷Pb<br>¹⁴C |-id=Radium-222 | rowspan=2|²²²Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 134 | rowspan=2|222.0153734(48) | rowspan=2|33.6(4)&nbsp;s | α | ²¹⁸Rn | rowspan=2|0+ | rowspan=2| |- | CD (3.0×10^{−8}%) | ²⁰⁸Pb<br>¹⁴C |- | rowspan=2|²²³Ra | rowspan=2|Actinium X | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 135 | rowspan=2|223.0185006(22) | rowspan=2|11.4352(10)&nbsp;d | α | ²¹⁹Rn | rowspan=2|3/2+ | rowspan=2|Trace |- | CD (8.9×10^{−8}%) | ²⁰⁹Pb<br>¹⁴C |-id=Radium-224 | rowspan=2|²²⁴Ra | rowspan=2|Thorium X | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 136 | rowspan=2|224.0202104(19) | rowspan=2|3.6316(14)&nbsp;d | α | ²²⁰Rn | rowspan=2|0+ | rowspan=2|Trace |- | CD (4.0×10^{−9}%) | ²¹⁰Pb<br>¹⁴C |-id=Radium-225 | rowspan=2|²²⁵Ra | rowspan=2| | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 137 | rowspan=2|225.0236105(28) | rowspan=2|14.82(19)&nbsp;d | β^− | ²²⁵Ac | rowspan=2|1/2+ | rowspan=2|Trace |- |α (0.0026%) |²²¹Rn |- | rowspan=2|²²⁶Ra | rowspan=2|Radium | rowspan=2 style="text-align:right" | 88 | rowspan=2 style="text-align:right" | 138 | rowspan=2|226.0254082(21) | rowspan=2|1600(7)&nbsp;y | α | ²²²Rn | rowspan=2|0+ | rowspan=2|Trace |- | CD (2.6×10^{−9}%) | ²¹²Pb<br>¹⁴C |-id=Radium-227 | ²²⁷Ra | | style="text-align:right" | 88 | style="text-align:right" | 139 | 227.0291762(21) | 42.2(5)&nbsp;min | β^− | ²²⁷Ac | 3/2+ | |-id=Radium-228 | ²²⁸Ra | Mesothorium 1 | style="text-align:right" | 88 | style="text-align:right" | 140 | 228.0310686(21) | 5.75(3)&nbsp;y | β^− | ²²⁸Ac | 0+ | Trace |-id=Radium-229 | ²²⁹Ra | | style="text-align:right" | 88 | style="text-align:right" | 141 | 229.034957(17) | 4.0(2)&nbsp;min | β^− | ²²⁹Ac | 5/2+ | |-id=Radium-230 | ²³⁰Ra | | style="text-align:right" | 88 | style="text-align:right" | 142 | 230.037055(11) | 93(2)&nbsp;min | β^− | ²³⁰Ac | 0+ | |-id=Radium-231 | ²³¹Ra | | style="text-align:right" | 88 | style="text-align:right" | 143 | 231.041027(12) | 104(1)&nbsp;s | β^− | ²³¹Ac | (5/2+) | |-id=Radium-231m | style="text-indent:1em" | ^231mRa | | colspan="3" style="text-indent:2em" | 66.21(9)&nbsp;keV | ~53&nbsp;μs | IT | ²³¹Ra | (1/2+) | |-id=Radium-232 | ²³²Ra | | style="text-align:right" | 88 | style="text-align:right" | 144 | 232.0434753(98) | 4.0(3)&nbsp;min | β^− | ²³²Ac | 0+ | |-id=Radium-233 | ²³³Ra | | style="text-align:right" | 88 | style="text-align:right" | 145 | 233.0475946(92) | 30(5)&nbsp;s | β^− | ²³³Ac | 1/2+# | |-id=Radium-234 | ²³⁴Ra | | style="text-align:right" | 88 | style="text-align:right" | 146 | 234.0503821(90) | 30(10)&nbsp;s | β^− | ²³⁴Ac | 0+ |

Actinides vs fission products

References

• Isotope masses from:
• Half-life, spin, and isomer data selected from the following sources.

Notes