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 1600 years. ²²⁶Ra occurs in the decay chain of ²³⁸U (often referred to as the radium series). Radium has 34 known isotopes from ²⁰¹Ra to ²³⁴Ra.

Isotopes of radium (₈₈Ra)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 223Ra trace 11.43 d α 219Rn 224Ra trace 3.6319 d α 220Rn 225Ra trace 14.9 d β− 225Ac α[2] 221Rn 226Ra trace 1599 y α 222Rn 228Ra trace 5.75 y β− 228Ac

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In the early history of the study of radioactivity, the different natural isotopes of radium were given different names, as it was not until Frederick Soddy's scientific career in the early 1900s that the concept of isotopes was realized.^[3] In this scheme, ²²³Ra was named actinium X (AcX), ²²⁴Ra thorium X (ThX), ²²⁶Ra radium (Ra), and ²²⁸Ra mesothorium 1 (MsTh₁).^[4] 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,^[5] though mesothorium 1 in particular was still used for some time, with a footnote explaining that it referred to ²²⁸Ra.^[6] Some of radium-226's decay products received historical names including "radium",^[7] ranging from radium A to radium G, with the letter indicating approximately how far they were down the chain from their parent ²²⁶Ra.^[a]

In 2013 it was discovered that the nucleus of radium-224 is pear-shaped.^[10] This was the first discovery of an asymmetrical nucleus.

List of isotopes

Nuclide [n 1]	Historic name	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life	Decay mode [n 4]	Daughter isotope [n 5]	Spin and parity [n 6][n 7]	Isotopic abundance
		Excitation energy[n 7]
201Ra[11]		88	113		8+40 −4 ms	α	197Rn	(3/2−)
201mRa[12]		260(30) keV			1.6+7.7 −0.7 ms	α	197mRn	(13/2+)
202Ra		88	114	202.00989(7)	3.8+1.3 −0.8 ms[11]	α	198Rn	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+
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+	Trace[n 8]
						CD (1.2×10−10%)[n 9]	207Pb 14C
222Ra		88	134	222.015375(5)	38.0(5) s	α	218Rn	0+
						CD (3×10−8%)	208Pb 14C
223Ra[n 10]	Actinium X	88	135	223.0185022(27)	11.43(5) d	α	219Rn	3/2+	Trace[n 11]
						CD (6.4×10−8%)	209Pb 14C
224Ra	Thorium X	88	136	224.0202118(24)	3.6319(23) d	α	220Rn	0+	Trace[n 12]
						CD (4.3×10−9%)	210Pb 14C
225Ra		88	137	225.023612(3)	14.9(2) d	β−	225Ac	1/2+	Trace[n 13]
						α (2.0×10−3%)[2]	221Rn
226Ra	Radium[n 14]	88	138	226.0254098(25)	1600(7) y	α[n 15]	222Rn	0+	Trace[n 16]
						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 12]
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+
This table header & footer: view

1. ^mRa – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. Modes of decay:

   CD:	Cluster decay
   EC:	Electron capture
   IT:	Isomeric transition

5. Bold symbol as daughter – Daughter product is stable.
6. ( ) spin value – Indicates spin with weak assignment arguments.
7. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
8. Intermediate decay product of ²³⁷Np
9. Lightest known nuclide to undergo cluster decay
10. Used for treating bone cancer
11. Intermediate decay product of ²³⁵U
12. Intermediate decay product of ²³²Th
13. Intermediate decay product of ²³⁷Np
14. Source of element's name
15. Theoretically capable of β^-β^- decay to ²²⁶Th^[1]
16. Intermediate decay product of ²³⁸U

Actinides vs fission products

Actinides and fission products by half-life v t e
Actinides[13] by decay chain				Half-life range (a)	Fission products of 235U by yield[14]
4n	4n + 1	4n + 2	4n + 3		4.5–7%	0.04–1.25%	<0.001%
228Ra№				4–6 a		155Euþ
248Bk[15]				> 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[16]	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[17]
232Th№		238U№	235Uƒ№	0.7–14.1 Ga
₡,  has thermal neutron capture cross section in the range of 8–50 barns ƒ,  fissile №,  primarily a naturally occurring radioactive material (NORM) þ,  neutron poison (thermal neutron capture cross section greater than 3k barns)

References

1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
2. Liang, C. F.; Paris, P.; Sheline, R. K. (2000-09-19). "α decay of ²²⁵Ra". Physical Review C. 62 (4). American Physical Society (APS): 047303. Bibcode:2000PhRvC..62d7303L. doi:10.1103/physrevc.62.047303. ISSN 0556-2813.
3. Nagel, Miriam C. (September 1982). "Frederick Soddy: From alchemy to isotopes". Journal of Chemical Education. 59 (9): 739. Bibcode:1982JChEd..59..739N. doi:10.1021/ed059p739. ISSN 0021-9584.
4. Kirby, H.W. & Salutsky, Murrell L. (December 1964). The Radiochemistry of Radium (Report). crediting UNT Libraries Government Documents Department. p. 3 – via University of North Texas, UNT Digital Library. Alternate source: https://sgp.fas.org/othergov/doe/lanl/lib-www/books/rc000041.pdf
5. Giunta, Carmen J. (2017). "ISOTOPES: IDENTIFYING THE BREAKTHROUGH PUBLICATION (1)" (PDF). Bull. Hist. Chem. 42 (2): 103–111.
6. Looney, William B. (1958). "Effects of Radium in Man". Science. 127 (3299): 630–633. Bibcode:1958Sci...127..630L. doi:10.1126/science.127.3299.630. ISSN 0036-8075. JSTOR 1755774. PMID 13529029.
7. Mitchell, S. A. "Is Radium in the Sun?". Popular Astronomy. 21: 321–331. Bibcode:1913PA.....21..321M.
8. Kuhn, W. (1929). "LXVIII. Scattering of thorium C" γ-radiation by radium G and ordinary lead". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 8 (52): 628. doi:10.1080/14786441108564923. ISSN 1941-5982.
9. Kinsey, R. R. (December 18, 1997), "The radioactive series of radium-226" (PDF), The NUDAT/PCNUDAT Program for Nuclear Data – via CERN
10. Hills, Stephanie (8 May 2013). "First observations of short-lived pear-shaped atomic nuclei". CERN.
11. Kalaninová, Z.; Antalic, S.; Andreyev, A. N.; Heßberger, F. P.; Ackermann, D.; Andel, B.; Bianco, L.; Hofmann, S.; Huyse, M.; Kindler, B.; Lommel, B.; Mann, R.; Page, R. D.; Sapple, P. J.; Thomson, J.; Van Duppen, P.; Venhart, M. (12 May 2014). "Decay of ^201–203Ra and ^200–202Fr" (PDF). Physical Review C. 89 (5): 054312. Bibcode:2014PhRvC..89e4312K. doi:10.1103/PhysRevC.89.054312. ISSN 0556-2813. Retrieved 11 June 2023.
12. Uusitalo, J.; Leino, M.; Enqvist, T.; Eskola, K.; Grahn, T.; Greenlees, P. T.; Jones, P.; Julin, R.; Juutinen, S.; Keenan, A.; Kettunen, H.; Koivisto, H.; Kuusiniemi, P.; Leppänen, A.-P.; Nieminen, P.; Pakarinen, J.; Rahkila, P.; Scholey, C. (11 February 2005). "α decay studies of very neutron-deficient francium and radium isotopes". Physical Review C. 71 (2): 024306. Bibcode:2005PhRvC..71b4306U. doi:10.1103/PhysRevC.71.024306. ISSN 0556-2813.
13. 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 nuclides have half-lives of at least four years (the longest-lived nuclide 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.
14. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
15. 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. Bibcode:1965NucPh..71..299M. 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 [years]. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
16. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
17. Excluding those "classically stable" nuclides with half-lives significantly in excess of ²³²Th; e.g., while ^113mCd has a half-life of only fourteen years, that of ¹¹³Cd is eight quadrillion years.

• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". 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.

Notes

1. Radium emanation = ²²²Rn, Ra A = ²¹⁸Po, Ra B = ²¹⁴Pb, Ra C = ²¹⁴Bi, Ra C₁ = ²¹⁴Po, Ra C₂ = ²¹⁰Tl, Ra D = ²¹⁰Pb, Ra E = ²¹⁰Bi, Ra F = ²¹⁰Po, and Ra G = ²⁰⁶Pb.^[8][9]