Isotopes of francium

Isotopes of francium (₈₇Fr)
α	208At
α	219At

Francium (₈₇Fr) has no stable isotopes. 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.

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) [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope	Spin and parity [n 6][n 4]	Isotopic abundance
Nuclide [n 1]	Historic name	Excitation energy[n 4]			Half-life [n 4]	Decay mode [n 5]	Daughter isotope	Spin and parity [n 6][n 4]	Isotopic abundance
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	199.00726(4)	16(7) ms	α	¹⁹⁵At	1/2+#
²⁰⁰Fr		87	113	200.00657(8)	24(10) ms	α	¹⁹⁶At	3+#
^200mFr		60(110) keV			190(120) ms	α	¹⁹⁶At	10−#
²⁰¹Fr		87	114	201.00386(8)	67(3) ms	α (99%)	¹⁹⁷At	(9/2−)
²⁰¹Fr		87	114	201.00386(8)	67(3) ms	β⁺ (1%)	²⁰¹Rn	(9/2−)
²⁰²Fr		87	115	202.00337(5)	290(30) ms	α (97%)	¹⁹⁸At	(3+)
²⁰²Fr		87	115	202.00337(5)	290(30) ms	β⁺ (3%)	²⁰²Rn	(3+)
^202mFr		330(90)# keV			340(40) ms	α (97%)	¹⁹⁸At	(10−)
^202mFr		330(90)# keV			340(40) ms	β⁺ (3%)	²⁰²Rn	(10−)
²⁰³Fr		87	116	203.000925(17)	0.55(2) s	α (95%)	¹⁹⁹At	(9/2−)#
²⁰³Fr		87	116	203.000925(17)	0.55(2) s	β⁺ (5%)	²⁰³Rn	(9/2−)#
²⁰⁴Fr		87	117	204.000653(26)	1.7(3) s	α (96%)	²⁰⁰At	(3+)
²⁰⁴Fr		87	117	204.000653(26)	1.7(3) s	β⁺ (4%)	²⁰⁴Rn	(3+)
^204m1Fr		50(4) keV			2.6(3) s	α (90%)	²⁰⁰At	(7+)
^204m1Fr		50(4) keV			2.6(3) s	β⁺ (10%)	²⁰⁴Rn	(7+)
^204m2Fr		326(4) keV			1.7(6) s			(10−)
²⁰⁵Fr		87	118	204.998594(8)	3.80(3) s	α (99%)	²⁰¹At	(9/2−)
²⁰⁵Fr		87	118	204.998594(8)	3.80(3) s	β⁺ (1%)	²⁰⁵Rn	(9/2−)
²⁰⁶Fr		87	119	205.99867(3)	~16 s	β⁺ (58%)	²⁰⁶Rn	(2+, 3+)
²⁰⁶Fr		87	119	205.99867(3)	~16 s	α (42%)	²⁰²At	(2+, 3+)
^206m1Fr		190(40) keV			15.9(1) s			(7+)
^206m2Fr		730(40) keV			700(100) ms			(10−)
²⁰⁷Fr		87	120	206.99695(5)	14.8(1) s	α (95%)	²⁰³At	9/2−
²⁰⁷Fr		87	120	206.99695(5)	14.8(1) s	β⁺ (5%)	²⁰⁷Rn	9/2−
²⁰⁸Fr		87	121	207.99714(5)	59.1(3) s	α (90%)	²⁰⁴At	7+
²⁰⁸Fr		87	121	207.99714(5)	59.1(3) s	β⁺ (10%)	²⁰⁸Rn	7+
²⁰⁹Fr		87	122	208.995954(16)	50.0(3) s	α (89%)	²⁰⁵At	9/2−
²⁰⁹Fr		87	122	208.995954(16)	50.0(3) s	β⁺ (11%)	²⁰⁹Rn	9/2−
²¹⁰Fr		87	123	209.996408(24)	3.18(6) min	α (60%)	²⁰⁶At	6+
²¹⁰Fr		87	123	209.996408(24)	3.18(6) min	β⁺ (40%)	²¹⁰Rn	6+
²¹¹Fr		87	124	210.995537(23)	3.10(2) min	α (80%)	²⁰⁷At	9/2−
²¹¹Fr		87	124	210.995537(23)	3.10(2) min	β⁺ (20%)	²¹¹Rn	9/2−
²¹²Fr		87	125	211.996202(28)	20.0(6) min	β⁺ (57%)	²¹²Rn	5+
²¹²Fr		87	125	211.996202(28)	20.0(6) min	α (43%)	²⁰⁸At	5+
²¹³Fr		87	126	212.996189(8)	34.14(6) s[2]	α (99.45%)	²⁰⁹At	9/2−
²¹³Fr		87	126	212.996189(8)	34.14(6) s[2]	β⁺ (.55%)	²¹³Rn	9/2−
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	215.000341(8)	86(5) ns	α	²¹¹At	9/2−
²¹⁶Fr		87	129	216.003198(15)	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	218.007578(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	219.009252(8)	20(2) ms	α	²¹⁵At	9/2−
²²⁰Fr		87	133	220.012327(4)	27.4(3) s	α (99.65%)	²¹⁶At	1+
²²⁰Fr		87	133	220.012327(4)	27.4(3) s	β⁻ (.35%)	²²⁰Ra	1+
²²¹Fr		87	134	221.014255(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	222.017552(23)	14.2(3) min	β⁻	²²²Ra	2−
²²³Fr	Actinium K	87	136	223.0197359(26)	22.00(7) min	β⁻ (99.99%)	²²³Ra	3/2(−)	Trace[n 10]
²²³Fr	Actinium K	87	136	223.0197359(26)	22.00(7) min	α (.006%)	²¹⁹At	3/2(−)	Trace[n 10]
²²⁴Fr		87	137	224.02325(5)	3.33(10) min	β⁻	²²⁴Ra	1−
²²⁵Fr		87	138	225.02557(3)	4.0(2) min	β⁻	²²⁵Ra	3/2−
²²⁶Fr		87	139	226.02939(11)	49(1) s	β⁻	²²⁶Ra	1−
²²⁷Fr		87	140	227.03184(11)	2.47(3) min	β⁻	²²⁷Ra	1/2+
²²⁸Fr		87	141	228.03573(22)#	38(1) s	β⁻	²²⁸Ra	2−
²²⁹Fr		87	142	229.03845(4)	50.2(4) s	β⁻	²²⁹Ra	(1/2+)#
²³⁰Fr		87	143	230.04251(48)#	19.1(5) s	β⁻	²³⁰Ra
²³¹Fr		87	144	231.04544(50)#	17.6(6) s	β⁻	²³¹Ra	(1/2+)#
²³²Fr		87	145	232.04977(69)#	5(1) s	β⁻	²³²Ra
²³³Fr		87	146	233.052518(21)	900(100) ms	β⁻	²³³Ra	1/2+ #
This table header & footer:

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

CD: Cluster decay

IT: Isomeric transition
( ) spin value – Indicates spin with weak assignment arguments.
Theoretically capable of β⁺ decay to ²¹⁶Rn[1]
Intermediate decay product of ²³⁷Np
The nuclide with the lowest atomic number known to undergo cluster decay
Intermediate decay product of ²³⁵U

References

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.
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.

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.

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[2] Fr – Excited nuclear isomer.

[3] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-4] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[TNN-5] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[6] Modes of decay:

CD: Cluster decay

IT: Isomeric transition

[7] ( ) spin value – Indicates spin with weak assignment arguments.

[9] Theoretically capable of β⁺ decay to ²¹⁶Rn[1]

[10] Intermediate decay product of ²³⁷Np

[11] The nuclide with the lowest atomic number known to undergo cluster decay

[12] Intermediate decay product of ²³⁵U

[NUBASE2020-1] 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.

[8] 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.

CD:	Cluster decay
IT:	Isomeric transition