Isotopes of francium

Francium (₈₇Fr) has no stable isotopes, thus a standard atomic weight cannot be given. Its most stable isotope is ²²³Fr with a half-life of 22 minutes, occurring in trace quantities in nature as an intermediate decay product of ²³⁵U.

Isotopes of francium (₈₇Fr)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 212Fr synth 20.0 min β+ 212Rn α 208At 221Fr trace 4.8 min α 217At 222Fr synth 14.2 min β− 222Ra 223Fr trace 22.00 min β− 223Ra α 219At

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Of elements whose most stable isotopes have been identified with certainty, francium is the most unstable. All elements with atomic number of 106 (seaborgium) or greater have most-stable-known isotopes shorter than that of francium, but as those elements have only a relatively small number of isotopes discovered, the possibility remains that undiscovered isotopes of these elements may have longer half-lives.

List of isotopes

Nuclide [n 1]	Historic name	Z	N	Isotopic mass (Da)[2] [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope	Spin and parity [n 6][n 4]	Isotopic abundance
		Excitation energy[n 4]
197Fr		87	110	197.01101(6)	2.3(19) ms	α	193At	(7/2−)
198Fr		87	111	198.01028(3)	15(3) ms	α	194At	3+#
199Fr		87	112	199.007269(15)	16(7) ms	α	195At	1/2+#
200Fr		87	113	200.00658(3)	24(10) ms	α	196At	3+#
200mFr		60(110) keV			190(120) ms	α	196At	10−#
201Fr		87	114	201.003852(10)	67(3) ms	α (99%)	197At	(9/2−)
						β+ (1%)	201Rn
202Fr		87	115	202.003330(6)	290(30) ms	α (97%)	198At	(3+)
						β+ (3%)	202Rn
202mFr		330(90)# keV			340(40) ms	α (97%)	198At	(10−)
						β+ (3%)	202Rn
203Fr		87	116	203.000941(7)	0.55(2) s	α (95%)	199At	(9/2−)#
						β+ (5%)	203Rn
204Fr		87	117	204.000652(26)	1.7(3) s	α (96%)	200At	(3+)
						β+ (4%)	204Rn
204m1Fr		50(4) keV			2.6(3) s	α (90%)	200At	(7+)
						β+ (10%)	204Rn
204m2Fr		326(4) keV			1.7(6) s			(10−)
205Fr		87	118	204.998594(8)	3.80(3) s	α (99%)	201At	(9/2−)
						β+ (1%)	205Rn
206Fr		87	119	205.998661(30)	~16 s	β+ (58%)	206Rn	(2+, 3+)
						α (42%)	202At
206m1Fr		190(40) keV			15.9(1) s			(7+)
206m2Fr		730(40) keV			700(100) ms			(10−)
207Fr		87	120	206.996941(19)	14.8(1) s	α (95%)	203At	9/2−
						β+ (5%)	207Rn
208Fr		87	121	207.997139(13)	59.1(3) s	α (90%)	204At	7+
						β+ (10%)	208Rn
209Fr		87	122	208.995940(12)	50.0(3) s	α (89%)	205At	9/2−
						β+ (11%)	209Rn
210Fr		87	123	209.996411(14)	3.18(6) min	α (60%)	206At	6+
						β+ (40%)	210Rn
211Fr		87	124	210.995555(13)	3.10(2) min	α (80%)	207At	9/2−
						β+ (20%)	211Rn
212Fr		87	125	211.996225(9)	20.0(6) min	β+ (57%)	212Rn	5+
						α (43%)	208At
213Fr		87	126	212.996184(5)	34.14(6) s[3]	α (99.45%)	209At	9/2−
						β+ (.55%)	213Rn
214Fr		87	127	213.998971(9)	5.0(2) ms	α	210At	(1−)
214m1Fr		123(6) keV			3.35(5) ms	α	210At	(8−)
214m2Fr		638(6) keV			103(4) ns			(11+)
214m3Fr		6477+Y keV			108(7) ns			(33+)
215Fr		87	128	215.000342(8)	86(5) ns	α	211At	9/2−
216Fr		87	129	216.003190(4)	0.70(2) μs	α	212At	(1−)
216mFr		219(6) keV			850(30) ns	α[n 7]	212At	(9−)
217Fr		87	130	217.004632(7)	16.8(19) μs	α	213At	9/2−
218Fr		87	131	218.007579(5)	1.0(6) ms	α	214At	1−
218m1Fr		86(4) keV			22.0(5) ms	α	214At	(8−)
218m2Fr		200(150)# keV						high
219Fr		87	132	219.009251(7)	20(2) ms	α	215At	9/2−
220Fr		87	133	220.012327(4)	27.4(3) s	α (99.65%)	216At	1+
						β− (.35%)	220Ra
221Fr		87	134	221.014254(5)	4.9(2) min	α (99.9%)	217At	5/2−	Trace[n 8]
						β− (.1%)	221Ra
						CD (8.79×10−11%)[n 9]	207Tl 14C
222Fr		87	135	222.017583(8)	14.2(3) min	β−	222Ra	2−
223Fr	Actinium K	87	136	223.0197342(21)	22.00(7) min	β− (99.99%)	223Ra	3/2(−)	Trace[n 10]
						α (.006%)	219At
224Fr		87	137	224.023348(12)	3.33(10) min	β−	224Ra	1−
225Fr		87	138	225.025572(13)	4.0(2) min	β−	225Ra	3/2−
226Fr		87	139	226.029545(7)	49(1) s	β−	226Ra	1−
227Fr		87	140	227.031865(6)	2.47(3) min	β−	227Ra	1/2+
228Fr		87	141	228.035839(7)	38(1) s	β−	228Ra	2−
229Fr		87	142	229.038291(5)	50.2(4) s	β−	229Ra	(1/2+)#
230Fr		87	143	230.042391(7)	19.1(5) s	β−	230Ra
231Fr		87	144	231.045175(8)	17.6(6) s	β−	231Ra	(1/2+)#
232Fr		87	145	232.049461(15)	5(1) s	β−	232Ra
233Fr		87	146	233.052518(21)	900(100) ms	β−	233Ra	1/2+ #
This table header & footer: view

1. ^mFr – 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. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   CD:	Cluster decay
   IT:	Isomeric transition

6. ( ) spin value – Indicates spin with weak assignment arguments.
7. Theoretically capable of β⁺ decay to ²¹⁶Rn^[1]
8. Intermediate decay product of ²³⁷Np
9. The nuclide with the lowest atomic number known to undergo cluster decay
10. Intermediate decay product of ²³⁵U

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. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
3. Fisichella, M.; Musumarra, A.; Farinon, F.; Nociforo, C.; Del Zoppo, A.; Figuera, P.; La Cognata, M.; Pellegriti, M. G.; Scuderi, V.; Torresi, D.; Strano, E. (2013-07-24). "Determination of the half-life of ²¹³Fr with high precision". Physical Review C. 88 (1). American Physical Society (APS): 011303. Bibcode:2013PhRvC..88a1303F. doi:10.1103/physrevc.88.011303. ISSN 0556-2813.

• 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.