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 33 known isotopes from ²⁰²Ra to ²³⁴Ra.

Main isotopes of radium (₈₈Ra)

Iso­tope 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 ^226Ra trace 1600 y α ^222Rn ^228Ra trace 5.75 y β^− ^228Ac

In 2013 it was discovered that the nucleus of radium-224 is pear-shaped.[1] This was the first discovery of an asymmetric 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]
^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+	Trace[n 8]
						CD (1.2×10^−10%)	^207Pb ^14C
^222Ra		88	134	222.015375(5)	38.0(5) s	α	^218Rn	0+
						CD (3×10^−8%)	^208Pb ^14C
^223Ra[n 9]	Actinium X	88	135	223.0185022(27)	11.43(5) d	α	^219Rn	3/2+	Trace[n 10]
						CD (6.4×10^−8%)	^209Pb ^14C
^224Ra	Thorium X	88	136	224.0202118(24)	3.6319(23) d	α	^220Rn	0+	Trace[n 11]
						CD (4.3×10^−9%)	^210Pb ^14C
^225Ra		88	137	225.023612(3)	14.9(2) d	β^−	^225Ac	1/2+	Trace[n 12]
^226Ra	Radium[n 13]	88	138	226.0254098(25)	1600(7) y	α	^222Rn	0+	Trace[n 14]
						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 11]
^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. ^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. Used for treating bone cancer
10. Intermediate decay product of ²³⁵U
11. Intermediate decay product of ²³²Th
12. Intermediate decay product of ²³⁷Np
13. Source of element's name
14. Intermediate decay product of ²³⁸U

Actinides vs fission products

Actinides and fission products by half-life
Actinides[2] by decay chain				Half-life range (a)	Fission products of ^235U by yield[3]
4n	4n+1	4n+2	4n+3
						4.5–7%	0.04–1.25%	<0.001%
^228Ra^№				4–6 a	†		^155Eu^þ
^244Cm^ƒ	^241Pu^ƒ	^250Cf	^227Ac^№	10–29 a		^90Sr	^85Kr	^113mCd^þ
^232U^ƒ		^238Pu^ƒ	^243Cm^ƒ	29–97 a		^137Cs	^151Sm^þ	^121mSn
^248Bk[4]	^249Cf^ƒ	^242mAm^ƒ		141–351 a	No fission products have a half-life in the range of 100–210 ka ...
	^241Am^ƒ		^251Cf^ƒ[5]	430–900 a
		^226Ra^№	^247Bk	1.3–1.6 ka
^240Pu	^229Th	^246Cm^ƒ	^243Am^ƒ	4.7–7.4 ka
	^245Cm^ƒ	^250Cm		8.3–8.5 ka
			^239Pu^ƒ	24.1 ka
		^230Th^№	^231Pa^№	32–76 ka
^236Np^ƒ	^233U^ƒ	^234U^№		150–250 ka	‡	^99Tc^₡	^126Sn
^248Cm		^242Pu		327–375 ka			^79Se^₡
				1.53 Ma		^93Zr
	^237Np^ƒ			2.1–6.5 Ma		^135Cs^₡	^107Pd
^236U			^247Cm^ƒ	15–24 Ma			^129I^₡
^244Pu				80 Ma	... nor beyond 15.7 Ma[6]
^232Th^№		^238U^№	^235U^ƒ№	0.7–14.1 Ga
Legend for superscript symbols ₡  has thermal neutron capture cross section in the range of 8–50 barns ƒ  fissile m  metastable isomer №  primarily a naturally occurring radioactive material (NORM) þ  neutron poison (thermal neutron capture cross section greater than 3k barns) †  range 4–97 a: Medium-lived fission product ‡  over 200 ka: Long-lived fission product

References

1. "First observations of short-lived pear-shaped atomic nuclei".
2. 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.
3. Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
4. 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]."
5. This is the heaviest nuclide with a half-life of at least four years before the "Sea of Instability".
6. 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 nearly 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
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• 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.