Isotopes of radium

Actinides and fission products by half-life
Actinides[1] by decay chain				Half-life range (y)	Fission products of ^235U by yield[2]
4n	4n+1	4n+2	4n+3
						4.5–7%	0.04–1.25%	<0.001%
^228Ra^№				4–6	†		^155Eu^þ
^244Cm^ƒ	^241Pu^ƒ	^250Cf	^227Ac^№	10–29		^90Sr	^85Kr	^113mCd^þ
^232U^ƒ		^238Pu^ƒ№	^243Cm^ƒ	29–97		^137Cs	^151Sm^þ	^121mSn
^248Bk[3]	^249Cf^ƒ	^242mAm^ƒ		141–351	No fission products have a half-life in the range of 100–210 k years ...
	^241Am^ƒ		^251Cf^ƒ[4]	430–900
		^226Ra^№	^247Bk	1.3 k – 1.6 k
^240Pu^ƒ№	^229Th^№	^246Cm^ƒ	^243Am^ƒ	4.7 k – 7.4 k
	^245Cm^ƒ	^250Cm		8.3 k – 8.5 k
			^239Pu^ƒ№	24.1 k
		^230Th^№	^231Pa^№	32 k – 76 k
^236Np^ƒ	^233U^ƒ№	^234U^№		150 k – 250 k	‡	^99Tc^₡	^126Sn
^248Cm		^242Pu^ƒ		327 k – 375 k			^79Se^₡
				1.53 M		^93Zr
	^237Np^ƒ№			2.1 M – 6.5 M		^135Cs^₡	^107Pd
^236U^№			^247Cm^ƒ	15 M – 24 M			^129I^₡
^244Pu^№				80 M	... nor beyond 15.7 M years[5]
^232Th^№		^238U^№	^235U^ƒ№	0.7 G – 14.1 G
Legend for superscript symbols ₡  has thermal neutron capture cross section in the range of 8–50 barns ƒ  fissile m  metastable isomer №  naturally occurring radioactive material (NORM) þ  neutron poison (thermal neutron capture cross section greater than 3k barns) †  range 4–97 y: Medium-lived fission product ‡  over 200,000 y: Long-lived fission product

Radium (Ra) has no stable or nearly stable isotopes, and thus a standard atomic mass cannot be given. The longest lived, and most common, isotope of radium is ²²⁶Ra with a half-life of 1,600 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.

Table

nuclide symbol	historic name	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[6][n 1]	daughter isotope(s)[n 2]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
		excitation energy
^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+
						CD (1.2×10^−10%)	^207Pb ^14C
^222Ra		88	134	222.015375(5)	38.0(5) s	α	^218Rn	0+	Trace[n 3]
						CD (3×10^−8%)	^208Pb ^14C
^223Ra[n 4]	Actinium X	88	135	223.0185022(27)	11.43(5) d	α	^219Rn	3/2+	Trace[n 5]
						CD (6.4×10^−8%)	^209Pb ^14C
^224Ra	Thorium X	88	136	224.0202118(24)	3.6319(23) d	α	^220Rn	0+	Trace[n 6]
						CD (4.3×10^−9%)	^210Pb ^14C
^225Ra		88	137	225.023612(3)	14.9(2) d	β^−	^225Ac	1/2+
^226Ra	Radium[n 7]	88	138	226.0254098(25)	1600(7) y	α	^222Rn	0+	[n 8]
						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 6]
^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. Abbreviations:
   CD: Cluster decay
   EC: Electron capture
   IT: Isomeric transition
2. Bold for stable isotopes
3. Intermediate decay product of ²³⁸U
4. Used for treating bone cancer
5. Intermediate decay product of ²³⁵U
6. Intermediate decay product of ²³²Th
7. Source of element's name
8. Intermediate decay product of ²³⁸U

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

References

1. 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 isotopes have half-lives of at least four years (the longest-lived isotope 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.
2. Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
3. 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. 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 y. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y."
4. This is the heaviest isotope with a half-life of at least four years before the "Sea of Instability".
5. Excluding those "classically stable" isotopes 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.
6. "Universal Nuclide Chart". nucleonica. (registration required (help)).

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). 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:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylo (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (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. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in: |access-date= (help)
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.