Isotopes of francium

Isotopes of francium (₈₇Fr)
α	208At
β−	221Ra
α	219At
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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.

Of elements whose most stable isotopes have been identified with certainty, francium is the most unstable, though astatine is the rarest in nature due to its naturally-occurring isotopes having even shorter half-lives and even smaller branching ratios.

The elements with atomic number of 106 (seaborgium) or greater have their longest known half-life of any isotope shorter than that of francium, but as those elements have only isotopes on the proton-rich side of beta stability discovered, there is a strong possibility that undiscovered isotopes of these elements will have longer half-lives that could exceed that of francium-223.

List of isotopes

Nuclide ^{[n 1]}	Historic name	Z	N	Isotopic mass (Da)^[2] ^{[n 2]}^{[n 3]}	Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope	Spin and parity^[1] ^{[n 6]}^{[n 4]}	Isotopic abundance
Nuclide ^{[n 1]}	Historic name	Excitation energy^{[n 4]}			Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope	Spin and parity^[1] ^{[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+#
^198mFr^{[n 7]}		0(50) keV			1.1(7) ms	α	¹⁹⁴At	(10−)
¹⁹⁹Fr		87	112	199.007269(15)	6.6(22) ms	α	¹⁹⁵At	1/2+#
^199m1Fr		45(13) keV			6.5(9) ms	α	¹⁹⁵At	7/2−#
^199m2Fr		250(50)# keV			2.2(12) ms	α	¹⁹⁵At	13/2+#
²⁰⁰Fr		87	113	200.00658(3)	47.5(28) ms	α	¹⁹⁶At	(3+)
^200m1Fr^{[n 7]}		50(60) keV			190(120) ms	α	¹⁹⁶At	10−#
^200m2Fr		150(50)# keV			790(360) ns
²⁰¹Fr		87	114	201.003852(10)	62.8(19) ms	α	¹⁹⁷At	9/2−
^201m1Fr		129(10) keV			24(6) ms	α	¹⁹⁷At	1/2+
^201m2Fr		289.5(4) keV			720(40) ns	IT	²⁰¹Fr	13/2+
²⁰²Fr		87	115	202.003330(6)	372(12) ms	α	¹⁹⁸At	3+
^202mFr		257(6) keV			286(13) ms	α	¹⁹⁸At	10−
^202mFr		257(6) keV			286(13) ms	IT (?%)	²⁰²Fr	10−
²⁰³Fr		87	116	203.000941(7)	550(10) ms	α	¹⁹⁹At	9/2−
^203m1Fr		361(6) keV			43(4) ms	IT (80%)	²⁰³Fr	1/2+
^203m1Fr		361(6) keV			43(4) ms	α (20%)	¹⁹⁹At	1/2+
^203m2Fr		426.0(10) keV			370(50) ns	IT	²⁰³Fr	13/2+
²⁰⁴Fr		87	117	204.000652(26)	1.75(26) s	α (96%)	²⁰⁰At	3+
²⁰⁴Fr		87	117	204.000652(26)	1.75(26) s	β⁺ (4%)	²⁰⁴Rn	3+
^204m1Fr		50(4) keV			2.41(19) s	α (90%)	²⁰⁰At	7+
^204m1Fr		50(4) keV			2.41(19) s	β⁺ (10%)	²⁰⁴Rn	7+
^204m2Fr		326(4) keV			1.65(15) s	α (53%)	²⁰⁰At	10−
^204m2Fr		326(4) keV			1.65(15) s	IT (47%)	²⁰⁴Fr	10−
²⁰⁵Fr		87	118	204.998594(8)	3.90(7) s	α (98.5%)	²⁰¹At	9/2−
²⁰⁵Fr		87	118	204.998594(8)	3.90(7) s	β⁺ (1.5%)	²⁰⁵Rn	9/2−
^205m1Fr		544.0(10) keV			80(20) ns	IT	²⁰⁵Fr	13/2+
^205m2Fr		609(6) keV			1.15(4) ms	IT	²⁰³Fr	(1/2+)
²⁰⁶Fr		87	119	205.998661(30)	~16 s	α (88.4%)	²⁰²At	3+
²⁰⁶Fr		87	119	205.998661(30)	~16 s	β⁺ (11.6%)	²⁰⁶Rn	3+
^206m1Fr		200(40) keV			~16 s	α (84.7%)	²⁰²At	7+
						β⁺ (?%)	²⁰⁶Rn
						IT (?%)	²⁰⁶Fr
^206m2Fr		730(40) keV			700(100) ms	IT (87%)	²⁰⁶Fr	10−
^206m2Fr		730(40) keV			700(100) ms	α (13%)	²⁰²At	10−
²⁰⁷Fr		87	120	206.996941(19)	14.8(1) s	α (95%)	²⁰³At	9/2−
²⁰⁷Fr		87	120	206.996941(19)	14.8(1) s	β⁺ (5%)	²⁰⁷Rn	9/2−
²⁰⁸Fr		87	121	207.997139(13)	59.1(3) s	α (89%)	²⁰⁴At	7+
²⁰⁸Fr		87	121	207.997139(13)	59.1(3) s	β⁺ (11%)	²⁰⁸Rn	7+
^208mFr		826.3(5) keV			432(11) ns	IT	²⁰⁸Fr	10−
²⁰⁹Fr		87	122	208.995940(12)	50.5(7) s	α (89%)	²⁰⁵At	9/2−
²⁰⁹Fr		87	122	208.995940(12)	50.5(7) s	β⁺ (11%)	²⁰⁹Rn	9/2−
^209mFr		4659.8(7) keV			420(18) ns	IT	²⁰⁹Fr	45/2−
²¹⁰Fr		87	123	209.996411(14)	3.18(6) min	α (71%)	²⁰⁶At	6+
²¹⁰Fr		87	123	209.996411(14)	3.18(6) min	β⁺ (29%)	²¹⁰Rn	6+
^210mFr		4417.2(10) keV			475(6) ns	IT	²¹⁰Fr	(23)+
²¹¹Fr		87	124	210.995555(13)	3.10(2) min	α (87%)	²⁰⁷At	9/2−
²¹¹Fr		87	124	210.995555(13)	3.10(2) min	β⁺ (13%)	²¹¹Rn	9/2−
^211m1Fr		2423.16(24) keV			146(14) ns	IT	²¹¹Fr	29/2+
^211m2Fr		4657.3(4) keV			124.5(12) ns	IT	²¹¹Fr	45/2−
²¹²Fr		87	125	211.996225(9)	20.0(6) min	β⁺ (57%)	²¹²Rn	5+
²¹²Fr		87	125	211.996225(9)	20.0(6) min	α (43%)	²⁰⁸At	5+
^212m1Fr		1551.4(3) keV			31.9(7) μs	IT	²¹²Fr	11+
^212m2Fr		2492.2(4) keV			604(28) ns	IT	²¹²Fr	15−
^212m3Fr		5854.7(6) keV			312(21) ns	IT	²¹²Fr	27−
^212m4Fr		8533.4(11) keV			23.6(21) μs	IT	²¹²Fr	34+#
²¹³Fr		87	126	212.996184(5)	34.14(6) s	α (99.44%)	²⁰⁹At	9/2−
²¹³Fr		87	126	212.996184(5)	34.14(6) s	β⁺ (0.56%)	²¹³Rn	9/2−
^213m1Fr		1590.41(18) keV			505(14) ns	IT	²¹³Fr	21/2−
^213m2Fr		2537.62(23) keV			238(6) ns	IT	²¹³Fr	29/2+
^213m3Fr		8094.8(7) keV			3.1(2) μs	IT	²¹³Fr	(65/2−)
²¹⁴Fr		87	127	213.998971(9)	5.51(13) ms	α	²¹⁰At	(1−)
^214m1Fr		121(5) keV			3.35(5) ms	α	²¹⁰At	(8−)
^214m2Fr		638(5) keV			103(4) ns	IT	²¹⁴Fr	(11+)
^214m3Fr		6577(100)# keV			108(7) ns	IT	²¹⁴Fr	(33+)
²¹⁵Fr		87	128	215.000342(8)	90(4) ns	α	²¹¹At	9/2−
²¹⁶Fr		87	129	216.003190(4)	700(20) ns	α	²¹²At	(1−)
^216mFr		219(6) keV			850(30) ns	α	^212m1At^[3]	(9−)
²¹⁷Fr		87	130	217.004632(7)	22(5) μs	α	²¹³At	9/2−
²¹⁸Fr		87	131	218.007579(5)	1.4(5) ms	α	²¹⁴At	1−
^218mFr		87(4) keV			21.9(5) ms	α	²¹⁴At	(8−)
²¹⁹Fr		87	132	219.009251(7)	22.5(17) 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⁻ (0.35%)	²²⁰Ra	1+
²²¹Fr		87	134	221.014254(5)	4.801(5) min	α	²¹⁷At	5/2−	Trace^{[n 8]}
						β⁻ (0.0048%)	²²¹Ra
						CD (8.8×10⁻¹¹%)^{[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⁻	²²³Ra	3/2−	Trace^{[n 10]}
²²³Fr	Actinium K	87	136	223.0197342(21)	22.00(7) min	α (0.006%)	²¹⁹At	3/2−	Trace^{[n 10]}
²²⁴Fr		87	137	224.023348(12)	3.33(10) min	β⁻	²²⁴Ra	1−
²²⁵Fr		87	138	225.025572(13)	3.95(14) min	β⁻	²²⁵Ra	3/2−
²²⁶Fr		87	139	226.029545(7)	48.5(7) 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−
^228mFr		1004(30) keV			180(110) s
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	2+#
²³¹Fr		87	144	231.045175(8)	17.6(6) s	β⁻	²³¹Ra	(1/2+)
²³²Fr		87	145	232.049461(15)	5.5(6) s	β⁻	²³²Ra	(5)
²³³Fr		87	146	233.052518(21)	900(100) ms	β⁻	²³³Ra	1/2+#
This table header & footer: view

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

α: Alpha decay

β⁺: Positron emission

β⁻: Beta decay

CD: Cluster decay

IT: Isomeric transition
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ ^a ^b Order of ground state and isomer is uncertain.
^ Intermediate decay product of ²³⁷Np
^ The nuclide with the lowest atomic number known to undergo cluster decay
^ Intermediate decay product of ²³⁵U

References

^ ^a ^b ^c ^d 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.
^ 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.
^ "²¹⁶Fr α decay (850)" (PDF). NNDC Chart of Nuclides.

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 3.0 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.

[2] Fr – Excited nuclear isomer.

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

[TMS-5] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[TNN-6] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[7] Modes of decay:

α: Alpha decay

β⁺: Positron emission

β⁻: Beta decay

CD: Cluster decay

IT: Isomeric transition

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

[order-9] Order of ground state and isomer is uncertain.

[11] Intermediate decay product of ²³⁷Np

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

[13] 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.

[AME2020_II-3] 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.

[10] "²¹⁶Fr α decay (850)" (PDF). NNDC Chart of Nuclides.

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