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.

Ra-226 nitrate (3x 1 mCi) - Photo by Dr Andrew R. Burgoyne - Oak Ridge National Laboratory

Ra-224 nitrate (21.4 mCi) - Photo by Dr Andrew R. Burgoyne - Oak Ridge National Laboratory

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)[11] [n 2][n 3]	Half-life[1]	Decay mode[1] [n 4]	Daughter isotope [n 5]	Spin and parity[1] [n 6][n 7]	Isotopic abundance
		Excitation energy[n 7]
201Ra		88	113	201.012815(22)	20(30) ms	α	197Rn	(3/2−)
201mRa		263(26) keV			6(5) ms	α	197Rn	13/2+
202Ra		88	114	202.009742(16)	4.1(11) ms	α	198Rn	0+
203Ra		88	115	203.009234(10)	36(13) ms	α	199Rn	3/2−
203mRa		246(14) keV			25(5) ms	α	199Rn	13/2+
204Ra		88	116	204.0065069(96)	60(9) ms	α (99.7%)	200Rn	0+
205Ra		88	117	205.006231(24)	220(50) ms	α	201Rn	3/2−
205mRa		263(25) keV			180(50) ms	α	201Rn	13/2+
206Ra		88	118	206.003828(19)	0.24(2) s	α	202Rn	0+
207Ra		88	119	207.003772(63)	1.38(18) s	α (86%)	203Rn	5/2−#
						β+ (14%)	207Fr
207mRa		560(60) keV			57(8) ms	IT (85#%)	207Ra	13/2+
						α (?%)	203Rn
208Ra		88	120	208.0018550(97)	1.110(45) s	α (87%)	204Rn	0+
						β+ (13%)	208Fr
208mRa		2147.4(4) keV			263(17) ns	IT	208Ra	(8+)
209Ra		88	121	209.0019949(62)	4.71(8) s	α (90%)	205Rn	5/2−
209mRa		882.4(7) keV			117(5) μs	α (90%)	205Rn	13/2+
						β+ (10%)	209Fr
210Ra		88	122	210.0004754(99)	4.0(1) s	α	206Rn	0+
210mRa		2050.9(7) keV			2.29(3) μs	IT	210Ra	8+
211Ra		88	123	211.0008930(53)	12.6(12) s	α	207Rn	5/2−
211mRa		1198.1(8) keV			9.5(3) μs	IT	211Ra	13/2+
212Ra		88	124	211.999787(11)	13.0(2) s	α (?%)	208Rn	0+
						β+ (?%)	212Fr
212m1Ra		1958.4(20) keV			9.3(9) μs	IT	212Ra	8+
212m2Ra		2613.3(20) keV			0.85(13) μs	IT	212Ra	11−
213Ra		88	125	213.000371(11)	2.73(5) min	α (87%)	209Rn	1/2−
						β+ (13%)	213Fr
213mRa		1768(4) keV			2.20(5) ms	IT (99.4%)	213Ra	(17/2−)
						α (0.6%)	209Rn
214Ra		88	126	214.0000996(56)	2.437(16) s	α (99.94%)	210Rn	0+
						β+ (0.059%)	214Fr
214m1Ra		1819.7(18) keV			118(7) ns	IT	214Ra	6+
214m2Ra		1865.2(18) keV			67.3(15) μs	IT (99.91%)	214Ra	8+
						α (0.09%)	210Rn
214m3Ra		2683.2(18) keV			295(7) ns	IT	214Ra	11−
214m4Ra		3478.4(18) keV			279(4) ns	IT	214Ra	14+
214m5Ra		4146.8(18) keV			225(4) ns	IT	214Ra	17−
214m6Ra		6577.0(18) keV			128(4) ns	IT	214Ra	(25−)
215Ra		88	127	215.0027182(77)	1.669(9) ms	α	211Rn	9/2+#
215m1Ra		1877.8(3) keV			7.31(13) μs	IT	215Ra	(25/2+)
215m2Ra		2246.9(4) keV			1.39(7) μs	IT	215Ra	(29/2−)
215m3Ra		3807(50)# keV			555(10) ns	IT	215Ra	(43/2−)
216Ra		88	128	216.0035335(86)	172(7) ns	α	212Rn	0+
						EC (<1×10−8%)	216Fr
217Ra		88	129	217.0063227(76)	1.95(12) μs	α	213Rn	(9/2+)
218Ra		88	130	218.007134(11)	25.91(14) μs	α	214Rn	0+
219Ra		88	131	219.0100847(73)	9(2) ms	α	215Rn	(7/2)+
219mRa		16.7(8) keV			10(3) ns	α	215Rn	(11/2)+
220Ra		88	132	220.0110275(82)	18.1(12) ms	α	216Rn	0+
221Ra		88	133	221.0139173(05)	25(4) s	α	217Rn	5/2+	Trace[n 8]
						CD (1.2×10−10%)[n 9]	207Pb 14C
222Ra		88	134	222.0153734(48)	33.6(4) s	α	218Rn	0+
						CD (3.0×10−8%)	208Pb 14C
223Ra[n 10]	Actinium X	88	135	223.0185006(22)	11.4352(10) d	α	219Rn	3/2+	Trace[n 11]
						CD (8.9×10−8%)	209Pb 14C
224Ra	Thorium X	88	136	224.0202104(19)	3.6316(14) d	α	220Rn	0+	Trace[n 12]
						CD (4.0×10−9%)	210Pb 14C
225Ra		88	137	225.0236105(28)	14.82(19) d	β−	225Ac	1/2+	Trace[n 13]
						α (2.6×10−3%)[2]	221Rn
226Ra	Radium[n 14]	88	138	226.0254082(21)	1600(7) y	α[n 15]	222Rn	0+	Trace[n 16]
						CD (2.6×10−9%)	212Pb 14C
227Ra		88	139	227.0291762(21)	42.2(5) min	β−	227Ac	3/2+
228Ra	Mesothorium 1	88	140	228.0310686(21)	5.75(3) y	β−	228Ac	0+	Trace[n 12]
229Ra		88	141	229.034957(17)	4.0(2) min	β−	229Ac	5/2+
230Ra		88	142	230.037055(11)	93(2) min	β−	230Ac	0+
231Ra		88	143	231.041027(12)	104(1) s	β−	231Ac	(5/2+)
231mRa		66.21(9) keV			~53 μs	IT	231Ra	(1/2+)
232Ra		88	144	232.0434753(98)	4.0(3) min	β−	232Ac	0+
233Ra		88	145	233.0475946(92)	30(5) s	β−	233Ac	1/2+#
234Ra		88	146	234.0503821(90)	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:

   EC:	Electron capture
   CD:	Cluster decay
   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
16. Intermediate decay product of ²³⁸U

Actinides vs fission products

Actinides and fission products by half-life v t e
Actinides[12] by decay chain				Half-life range (a)	Fission products of 235U by yield[13]
4n	4n + 1	4n + 2	4n + 3		4.5–7%	0.04–1.25%	<0.001%
228Ra№				4–6 a		155Euþ
248Bk[14]				> 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[15]	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[16]
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)