鐳没有稳定或长寿命的同位素，故无法给出它的标准原子量。镭有从202Ra到234Ra共33种同位素，其中最稳定也最常见的同位素是半衰期1600年的226Ra。
2013年发现镭-224的原子核呈梨形，首次发现不对称原子核。
圖表
|-
| 202Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 114
| 202.00989(7)
| 2.6(21) ms
[0.7(+33−3) ms]
|
|
| 0+
|
|-
| rowspan=2|203Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 115
| rowspan=2|203.00927(9)
| rowspan=2|4(3) ms
|
| 199Rn
| rowspan=2|(3/2−)
| rowspan=2|
|-
| （不常見）
| 203Fr
|-
| rowspan=2 style="text-indent:1em" | 203mRa
| rowspan=2|
| rowspan=2 colspan="3" style="text-indent:2em" | 220(90) keV
| rowspan=2|41(17) ms
|
| 199Rn
| rowspan=2|(13/2+)
| rowspan=2|
|-
| （不常見）
| 203Fr
|-
| rowspan=2|204Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 116
| rowspan=2|204.006500(17)
| rowspan=2|60(11) ms
[59(+12−9) ms]
| (99.7%)
| 200Rn
| rowspan=2|0+
| rowspan=2|
|-
| (.3%)
| 204Fr
|-
| rowspan=2|205Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 117
| rowspan=2|205.00627(9)
| rowspan=2|220(40) ms
[210(+60−40) ms]
|
| 201Rn
| rowspan=2|(3/2−)
| rowspan=2|
|-
| （不常見）
| 205Fr
|-
| rowspan=2 style="text-indent:1em" | 205mRa
| rowspan=2|
| rowspan=2 colspan="3" style="text-indent:2em" | 310(110)# keV
| rowspan=2|180(50) ms
[170(+60−40) ms]
|
| 201Rn
| rowspan=2|(13/2+)
| rowspan=2|
|-
| IT （不常見）
| 205Ra
|-
| 206Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 118
| 206.003827(19)
| 0.24(2) s
|
| 202Rn
| 0+
|
|-
| rowspan=2|207Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 119
| rowspan=2|207.00380(6)
| rowspan=2|1.3(2) s
| (90%)
| 203Rn
| rowspan=2|(5/2−,3/2−)
| rowspan=2|
|-
| (10%)
| 207Fr
|-
| rowspan=3 style="text-indent:1em" | 207mRa
| rowspan=3|
| rowspan=3 colspan="3" style="text-indent:2em" | 560(50) keV
| rowspan=3|57(8) ms
| IT (85%)
| 207Ra
| rowspan=3|(13/2+)
| rowspan=3|
|-
| (15%)
| 203Rn
|-
| (.55%)
| 207Fr
|-
| rowspan=2|208Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 120
| rowspan=2|208.001840(17)
| rowspan=2|1.3(2) s
| (95%)
| 204Rn
| rowspan=2|0+
| rowspan=2|
|-
| (5%)
| 208Fr
|-
| style="text-indent:1em" | 208mRa
|
| colspan="3" style="text-indent:2em" | 1800(200) keV
| 270 ns
|
|
| (8+)
|
|-
| rowspan=2|209Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 121
| rowspan=2|209.00199(5)
| rowspan=2|4.6(2) s
| (90%)
| 205Rn
| rowspan=2|5/2−
| rowspan=2|
|-
| (10%)
| 209Fr
|-
| rowspan=2|210Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 122
| rowspan=2|210.000495(16)
| rowspan=2|3.7(2) s
| (96%)
| 206Rn
| rowspan=2|0+
| rowspan=2|
|-
| (4%)
| 210Fr
|-
| style="text-indent:1em" | 210mRa
|
| colspan="3" style="text-indent:2em" | 1800(200) keV
| 2.24 µs
|
|
| (8+)
|
|-
| rowspan=2|211Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 123
| rowspan=2|211.000898(28)
| rowspan=2|13(2) s
| (97%)
| 207Rn
| rowspan=2|5/2(−)
| rowspan=2|
|-
| (3%)
| 211Fr
|-
| rowspan=2|212Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 124
| rowspan=2|211.999794(12)
| rowspan=2|13.0(2) s
| (85%)
| 208Rn
| rowspan=2|0+
| rowspan=2|
|-
| (15%)
| 212Fr
|-
| style="text-indent:1em" | 212m1Ra
|
| colspan="3" style="text-indent:2em" | 1958.4(5) keV
| 10.9(4) µs
|
|
| (8)+
|
|-
| style="text-indent:1em" | 212m2Ra
|
| colspan="3" style="text-indent:2em" | 2613.4(5) keV
| 0.85(13) µs
|
|
| (11)−
|
|-
| rowspan=2|213Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 125
| rowspan=2|213.000384(22)
| rowspan=2|2.74(6) min
| (80%)
| 209Rn
| rowspan=2|1/2−
| rowspan=2|
|-
| (20%)
| 213Fr
|-
| rowspan=2 style="text-indent:1em" | 213mRa
| rowspan=2|
| rowspan=2 colspan="3" style="text-indent:2em" | 1769(6) keV
| rowspan=2|2.1(1) ms
| IT (99%)
| 213Ra
| rowspan=2|17/2−#
| rowspan=2|
|-
| (1%)
| 209Rn
|-
| rowspan=2|214Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 126
| rowspan=2|214.000108(10)
| rowspan=2|2.46(3) s
| (99.94%)
| 210Rn
| rowspan=2|0+
| rowspan=2|
|-
| (.06%)
| 214Fr
|-
| 215Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 127
| 215.002720(8)
| 1.55(7) ms
|
| 211Rn
| (9/2+)#
|
|-
| style="text-indent:1em" | 215m1Ra
|
| colspan="3" style="text-indent:2em" | 1877.8(5) keV
| 7.1(2) µs
|
|
| (25/2+)
|
|-
| style="text-indent:1em" | 215m2Ra
|
| colspan="3" style="text-indent:2em" | 2246.9(5) keV
| 1.39(7) µs
|
|
| (29/2−)
|
|-
| style="text-indent:1em" | 215m3Ra
|
| colspan="3" style="text-indent:2em" | 3756.6(6)+X keV
| 0.555(10) µs
|
|
| (43/2−)
|
|-
| rowspan=2|216Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 128
| rowspan=2|216.003533(9)
| rowspan=2|182(10) ns
|
| 212Rn
| rowspan=2|0+
| rowspan=2|
|-
| (1×10−8%)
| 216Fr
|-
| 217Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 129
| 217.006320(9)
| 1.63(17) µs
|
| 213Rn
| (9/2+)
|
|-
|218Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 130
|218.007140(12)
|25.2(3) µs
|
| 214Rn
|0+
|
|-
| 219Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 131
| 219.010085(9)
| 10(3) ms
|
| 215Rn
| (7/2)+
|
|-
| 220Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 132
| 220.011028(10)
| 17.9(14) ms
|
| 216Rn
| 0+
|
|-
| rowspan=2|221Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 133
| rowspan=2|221.013917(5)
| rowspan=2|28(2) s
|
| 217Rn
| rowspan=2|5/2+
| rowspan=2|
|-
| (1.2×10−10%)
| **'
|-
| rowspan=2|222Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 134
| rowspan=2|222.015375(5)
| rowspan=2|38.0(5) s
|
| 218Rn
| rowspan=2|0+
| rowspan=2|痕量
| rowspan=2|Actinium X
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 135
| rowspan=2|223.0185022(27)
| rowspan=2|11.43(5) d
|
| 219Rn
| rowspan=2|3/2+
| rowspan=2|痕量
|-
| (6.4×10−8%)
|
|-
| rowspan=2|224Ra
| rowspan=2|Thorium X
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 136
| rowspan=2|224.0202118(24)
| rowspan=2|3.6319(23) d
|
| 220Rn
| rowspan=2|0+
| rowspan=2|痕量
|-
| (4.3×10−9%)
|
|-
| rowspan=2| 225Ra
| rowspan=2|
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 137
| rowspan=2| 225.023612(3)
| rowspan=2| 14.9(2) d
|
| 225Ac
| rowspan=2| 1/2+
| rowspan=2|痕量
|-
|（0.0026%）
| rowspan=2 style="text-align:right" | 88
| rowspan=2 style="text-align:right" | 138
| rowspan=2|226.0254098(25)
| rowspan=2|1600(7) y
|
| 222Rn
| rowspan=2|0+
| rowspan=2|痕量
|-
| (2.6×10−9%)
|
|-
| 227Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 139
| 227.0291778(25)
| 42.2(5) min
|
| 227Ac
| 3/2+
|
|-
| 228Ra
| Mesothorium 1
| style="text-align:right" | 88
| style="text-align:right" | 140
| 228.0310703(26)
| 5.75(3) y
|
| 228Ac
| 0+
| 痕量
|-
| 229Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 141
| 229.034958(20)
| 4.0(2) min
|
| 229Ac
| 5/2(+)
|
|-
| 230Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 142
| 230.037056(13)
| 93(2) min
|
| 230Ac
| 0+
|
|-
| 231Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 143
| 231.04122(32)#
| 103(3) s
|
| 231Ac
| (5/2+)
|
|-
| style="text-indent:1em" | 231mRa
|
| colspan="3" style="text-indent:2em" | 66.21(9) keV
| ~53 µs
|
|
| (1/2+)
|
|-
| 232Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 144
| 232.04364(30)#
| 250(50) s
|
| 232Ac
| 0+
|
|-
| 233Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 145
| 233.04806(50)#
| 30(5) s
|
| 233Ac
| 1/2+#
|
|-
| 234Ra
|
| style="text-align:right" | 88
| style="text-align:right" | 146
| 234.05070(53)#
| 30(10) s
|
| 234Ac
| 0+
|
|}
参考文獻
- Isotope masses from [https://web.archive.org/web/20080923134436/http://www.nndc.bnl.gov/amdc/index.html Ame2003 Atomic Mass Evaluation] by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
** Audi, Bersillon, Blachot, Wapstra. [http://amdc.in2p3.fr/web/nubase_en.html The Nubase2003 evaluation of nuclear and decay properties] , Nuc. Phys. A 729, pp. 3-128 (2003).
** National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the [http://www.nndc.bnl.gov/nudat2/ NuDat 2.1 database] (retrieved Sept. 2005).
* David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition*, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
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