Isotopes of francium

Francium (₈₇Fr) has no stable isotopes, so 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.

Quick facts Main isotopes, Decay ...

Isotopes of francium (₈₇Fr)

Main isotopes^[1]			Decay
Isotope	abundance	half-life (t_1/2)	mode	product
²¹²Fr	synth	20.0 min	β⁺	²¹²Rn
²¹²Fr	synth	20.0 min	α	²⁰⁸At
²²¹Fr	trace	4.801 min	α	²¹⁷At
²²¹Fr	trace	4.801 min	β⁻	²²¹Ra
²²²Fr	synth	14.2 min	β⁻	²²²Ra
²²³Fr	trace	22.00 min	β⁻	²²³Ra
²²³Fr	trace	22.00 min	α	²¹⁹At

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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

More information Nuclide, Historic name ...

Nuclide ^{[n 1]}	Historic name	Z	N	Isotopic mass (Da)^[2] ^{[n 2]}^{[n 3]}	Discovery year^[3]^[4]	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]}			Discovery year^[3]^[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)	2013	2.3(19) ms	α	¹⁹³At	(7/2−)
¹⁹⁸Fr		87	111	198.01028(3)	2013	15(3) ms	α	¹⁹⁴At	3+#
^198mFr^{[n 7]}		0(50) keV			2013	1.1(7) ms	α	¹⁹⁴At	(10−)
¹⁹⁹Fr		87	112	199.007269(15)	1999	6.6(22) ms	α	¹⁹⁵At	1/2+#
^199m1Fr		45(13) keV			2013	6.5(9) ms	α	¹⁹⁵At	7/2−#
^199m2Fr		250(50)# keV			2013	2.2(12) ms	α	¹⁹⁵At	13/2+#
²⁰⁰Fr		87	113	200.00658(3)	1995	47.5(28) ms	α	¹⁹⁶At	(3+)
^200m1Fr^{[n 7]}		50(60) keV			2014	190(120) ms	α	¹⁹⁶At	10−#
^200m2Fr		150(50)# keV			(2014)^{[n 8]}	790(360) ns
²⁰¹Fr		87	114	201.003852(10)	1980	62.8(19) ms	α	¹⁹⁷At	9/2−
^201m1Fr		129(10) keV			2005	24(6) ms	α	¹⁹⁷At	1/2+
^201m2Fr		289.5(4) keV			2014	720(40) ns	IT	²⁰¹Fr	13/2+
²⁰²Fr		87	115	202.003330(6)	1980	372(12) ms	α	¹⁹⁸At	3+
^202mFr		257(6) keV			1992	286(13) ms	α	¹⁹⁸At	10−
^202mFr		257(6) keV			1992	286(13) ms	IT (?%)	²⁰²Fr	10−
²⁰³Fr		87	116	203.000941(7)	1967	550(10) ms	α	¹⁹⁹At	9/2−
^203m1Fr		361(6) keV			2013	43(4) ms	IT (80%)	²⁰³Fr	1/2+
^203m1Fr		361(6) keV			2013	43(4) ms	α (20%)	¹⁹⁹At	1/2+
^203m2Fr		426.0(10) keV			2013	370(50) ns	IT	²⁰³Fr	13/2+
²⁰⁴Fr		87	117	204.000652(26)	1964	1.75(26) s	α (96%)	²⁰⁰At	3+
²⁰⁴Fr		87	117	204.000652(26)	1964	1.75(26) s	β⁺ (4%)	²⁰⁴Rn	3+
^204m1Fr		50(4) keV			1967	2.41(19) s	α (90%)	²⁰⁰At	7+
^204m1Fr		50(4) keV			1967	2.41(19) s	β⁺ (10%)	²⁰⁴Rn	7+
^204m2Fr		326(4) keV			1992	1.65(15) s	α (53%)	²⁰⁰At	10−
^204m2Fr		326(4) keV			1992	1.65(15) s	IT (47%)	²⁰⁴Fr	10−
²⁰⁵Fr		87	118	204.998594(8)	1964	3.90(7) s	α (98.5%)	²⁰¹At	9/2−
²⁰⁵Fr		87	118	204.998594(8)	1964	3.90(7) s	β⁺ (1.5%)	²⁰⁵Rn	9/2−
^205m1Fr		544.0(10) keV			2012	80(20) ns	IT	²⁰⁵Fr	13/2+
^205m2Fr		609(6) keV			2012	1.15(4) ms	IT	²⁰³Fr	(1/2+)
²⁰⁶Fr		87	119	205.998661(30)	1964	~16 s	α (88.4%)	²⁰²At	3+
²⁰⁶Fr		87	119	205.998661(30)	1964	~16 s	β⁺ (11.6%)	²⁰⁶Rn	3+
^206m1Fr		200(40) keV			1981	~16 s	α (84.7%)	²⁰²At	7+
							β⁺ (?%)	²⁰⁶Rn
							IT (?%)	²⁰⁶Fr
^206m2Fr		730(40) keV			1981	700(100) ms	IT (87%)	²⁰⁶Fr	10−
^206m2Fr		730(40) keV			1981	700(100) ms	α (13%)	²⁰²At	10−
²⁰⁷Fr		87	120	206.996941(19)	1964	14.8(1) s	α (95%)	²⁰³At	9/2−
²⁰⁷Fr		87	120	206.996941(19)	1964	14.8(1) s	β⁺ (5%)	²⁰⁷Rn	9/2−
²⁰⁸Fr		87	121	207.997139(13)	1964	59.1(3) s	α (89%)	²⁰⁴At	7+
²⁰⁸Fr		87	121	207.997139(13)	1964	59.1(3) s	β⁺ (11%)	²⁰⁸Rn	7+
^208mFr		826.3(5) keV			2009	432(11) ns	IT	²⁰⁸Fr	10−
²⁰⁹Fr		87	122	208.995940(12)	1964	50.5(7) s	α (89%)	²⁰⁵At	9/2−
²⁰⁹Fr		87	122	208.995940(12)	1964	50.5(7) s	β⁺ (11%)	²⁰⁹Rn	9/2−
^209mFr		4659.8(7) keV			2006	420(18) ns	IT	²⁰⁹Fr	45/2−
²¹⁰Fr		87	123	209.996411(14)	1964	3.18(6) min	α (71%)	²⁰⁶At	6+
²¹⁰Fr		87	123	209.996411(14)	1964	3.18(6) min	β⁺ (29%)	²¹⁰Rn	6+
^210mFr		4417.2(10) keV			2016	475(6) ns	IT	²¹⁰Fr	(23)+
²¹¹Fr		87	124	210.995555(13)	1964	3.10(2) min	α (87%)	²⁰⁷At	9/2−
²¹¹Fr		87	124	210.995555(13)	1964	3.10(2) min	β⁺ (13%)	²¹¹Rn	9/2−
^211m1Fr		2423.16(24) keV			1986	146(14) ns	IT	²¹¹Fr	29/2+
^211m2Fr		4657.3(4) keV			1986	124.5(12) ns	IT	²¹¹Fr	45/2−
²¹²Fr		87	125	211.996225(9)	1950	20.0(6) min	β⁺ (57%)	²¹²Rn	5+
²¹²Fr		87	125	211.996225(9)	1950	20.0(6) min	α (43%)	²⁰⁸At	5+
^212m1Fr		1551.4(3) keV			1990	31.9(7) μs	IT	²¹²Fr	11+
^212m2Fr		2492.2(4) keV			1977	604(28) ns	IT	²¹²Fr	15−
^212m3Fr		5854.7(6) keV			1986	312(21) ns	IT	²¹²Fr	27−
^212m4Fr		8533.4(11) keV			1990	23.6(21) μs	IT	²¹²Fr	34+#
²¹³Fr		87	126	212.996184(5)	1964	34.14(6) s	α (99.44%)	²⁰⁹At	9/2−
²¹³Fr		87	126	212.996184(5)	1964	34.14(6) s	β⁺ (0.56%)	²¹³Rn	9/2−
^213m1Fr		1590.41(18) keV			1976	505(14) ns	IT	²¹³Fr	21/2−
^213m2Fr		2537.62(23) keV			1976	238(6) ns	IT	²¹³Fr	29/2+
^213m3Fr		8094.8(7) keV			1989	3.1(2) μs	IT	²¹³Fr	(65/2−)
²¹⁴Fr		87	127	213.998971(9)	1966	5.51(13) ms	α	²¹⁰At	(1−)
^214m1Fr		121(5) keV			1968	3.35(5) ms	α	²¹⁰At	(8−)
^214m2Fr		638(5) keV			1994	103(4) ns	IT	²¹⁴Fr	(11+)
^214m3Fr		6577(100)# keV			1994	108(7) ns	IT	²¹⁴Fr	(33+)
²¹⁵Fr		87	128	215.000342(8)	1970	90(4) ns	α	²¹¹At	9/2−
²¹⁶Fr		87	129	216.003190(4)	1970	700(20) ns	α	²¹²At	(1−)
^216mFr		219(6) keV			2007	850(30) ns	α	^212m1At^[5]	(9−)
²¹⁷Fr		87	130	217.004632(7)	1968	22(5) μs	α	²¹³At	9/2−
²¹⁸Fr		87	131	218.007579(5)	1949	1.4(5) ms	α	²¹⁴At	1−
^218mFr		87(4) keV			1982	21.9(5) ms	α	²¹⁴At	(8−)
²¹⁹Fr		87	132	219.009251(7)	1948	22.5(17) ms	α	²¹⁵At	9/2−
²²⁰Fr		87	133	220.012327(4)	1948	27.4(3) s	α (99.65%)	²¹⁶At	1+
²²⁰Fr		87	133	220.012327(4)	1948	27.4(3) s	β⁻ (0.35%)	²²⁰Ra	1+
²²¹Fr		87	134	221.014254(5)	1947	4.801(5) min	α	²¹⁷At	5/2−	Trace^{[n 9]}
							β⁻ (0.0048%)	²²¹Ra
							CD (8.8×10⁻¹¹%)^{[n 10]}	²⁰⁷Tl ¹⁴C
²²²Fr		87	135	222.017583(8)	1975	14.2(3) min	β⁻^{[n 11]}	²²²Ra	2−
²²³Fr	Actinium K	87	136	223.0197342(21)	1939	22.00(7) min	β⁻	²²³Ra	3/2−	Trace^{[n 12]}
²²³Fr	Actinium K	87	136	223.0197342(21)	1939	22.00(7) min	α (0.006%)	²¹⁹At	3/2−	Trace^{[n 12]}
²²⁴Fr		87	137	224.023348(12)	1969	3.33(10) min	β⁻	²²⁴Ra	1−
²²⁵Fr		87	138	225.025572(13)	1969	3.95(14) min	β⁻	²²⁵Ra	3/2−
²²⁶Fr		87	139	226.029545(7)	1969	48.5(7) s	β⁻	²²⁶Ra	1−
²²⁷Fr		87	140	227.031865(6)	1972	2.47(3) min	β⁻	²²⁷Ra	1/2+
²²⁸Fr		87	141	228.035839(7)	1972	38(1) s	β⁻	²²⁸Ra	2−
^228mFr		1004(30) keV			(2008)^{[n 13]}	180(110) s
²²⁹Fr		87	142	229.038291(5)	1975	50.2(4) s	β⁻	²²⁹Ra	(1/2+)
²³⁰Fr		87	143	230.042391(7)	1987	19.1(5) s	β⁻	²³⁰Ra	2+#
²³¹Fr		87	144	231.045175(8)	1985	17.6(6) s	β⁻	²³¹Ra	(1/2+)
²³²Fr		87	145	232.049461(15)	1990	5.5(6) s	β⁻	²³²Ra	(5)
²³³Fr		87	146	233.052518(21)	2010	900(100) ms	β⁻	²³³Ra	1/2+#
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[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:

α: Alpha decay

β⁺: Positron emission

β⁻: Beta decay

CD: Cluster decay

IT: Isomeric transition
[6]
( ) spin value – Indicates spin with weak assignment arguments.
[7]
Order of ground state and isomer is uncertain.
[8]
Isomer had only been suggested, not included in discovery database
[9]
Intermediate decay product of ²³⁷Np
[10]
The nuclide with the lowest atomic number known to undergo cluster decay
[11]
Theoretically capable of α decay to ²¹⁸At with a partial half-life of ~1 d (branching ratio ~1%).^[6]
[12]
Intermediate decay product of ²³⁵U
[13]
Only published in a conference proceeding and not a refereed journal

Isotopes of francium

List of isotopes

References

Related Articles

α:	Alpha decay
β⁺:	Positron emission
β⁻:	Beta decay
CD:	Cluster decay
IT:	Isomeric transition