Isotopes of francium

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 as an intermediate decay product of ²³⁵U.

Main isotopes of francium (₈₇Fr)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^212Fr syn 20.0 min β^+ ^212Rn α ^208At ^221Fr trace 4.8 min α ^217At ^222Fr syn 14.2 min β^− ^222Ra ^223Fr trace 22.00 min β^− ^223Ra α ^219At

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 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
		Excitation energy[n 4]
^199Fr		87	112	199.00726(4)	16(7) ms			1/2+#
^200Fr		87	113	200.00657(8)	24(10) ms	α	^196At	3+#
^200mFr		60(110) keV			650(210) ms	α	^196At	10−#
						IT (rare)	^200Fr
^201Fr		87	114	201.00386(8)	67(3) ms	α (99%)	^197At	(9/2−)
						β^+ (1%)	^201Rn
^202Fr		87	115	202.00337(5)	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	203.000925(17)	0.55(2) s	α (95%)	^199At	(9/2−)#
						β^+ (5%)	^203Rn
^204Fr		87	117	204.000653(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	205.99867(3)	~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	206.99695(5)	14.8(1) s	α (95%)	^203At	9/2−
						β^+ (5%)	^207Rn
^208Fr		87	121	207.99714(5)	59.1(3) s	α (90%)	^204At	7+
						β^+ (10%)	^208Rn
^209Fr		87	122	208.995954(16)	50.0(3) s	α (89%)	^205At	9/2−
						β^+ (11%)	^209Rn
^210Fr		87	123	209.996408(24)	3.18(6) min	α (60%)	^206At	6+
						β^+ (40%)	^210Rn
^211Fr		87	124	210.995537(23)	3.10(2) min	α (80%)	^207At	9/2−
						β^+ (20%)	^211Rn
^212Fr		87	125	211.996202(28)	20.0(6) min	β^+ (57%)	^212Rn	5+
						α (43%)	^208At
^213Fr		87	126	212.996189(8)	34.6(3) s	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	215.000341(8)	86(5) ns	α	^211At	9/2−
^216Fr		87	129	216.003198(15)	0.70(2) µs	α	^212At	(1−)
						β^+ (2×10^−7%)	^216Rn
^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
						IT (rare)	^218Fr
^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+
						β^− (.35%)	^220Ra
^221Fr		87	134	221.014255(5)	4.9(2) min	α (99.9%)	^217At	5/2−	Trace[n 7]
						β^− (.1%)	^221Ra
						CD (8.79×10^−11%)	^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 8]
						α (.006%)	^219At
^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

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. Intermediate decay product of ²³⁷Np
8. Intermediate decay product of ²³⁵U

References

• 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
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• 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.