Isotopes of polonium

Isotopes of polonium (₈₄Po)
α 5.45%	202Pb
β+<0.01%	208Bi
β+0.454%	209Bi
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Last updated August 17, 2025

There are 42 known isotopes of polonium (₈₄Po), all radioactive, stretching from ¹⁸⁶Po to ²²⁷Po. The isotopes 210 through 218 occur naturally in the four principal decay chains; of these, ²¹⁰Po with a half-life of 138.376 days has the longest half-life and is, therefore, the most abundant by mass. It is also the most easily synthesized isotope, by neutron capture on natural bismuth, and so by far the most abundant artificial isotope as well.

Two other isotopes have longer lives: ²⁰⁹Po with a half-life of 124 years and ²⁰⁸Po with a half-life of 2.898 years. Both are made by using a cyclotron to bombard bismuth with protons.^[2]

List of isotopes

Nuclide ^{[n 1]}	Historic name	Z	N	Isotopic mass (Da)^[3] ^{[n 2]}^{[n 3]}	Half-life ^[1]	Decay mode ^[1]	Daughter isotope ^{[n 4]}^{[n 5]}	Spin and parity ^[1] ^{[n 6]}^{[n 7]}	Isotopic abundance
Nuclide ^{[n 1]}	Historic name	Excitation energy^{[n 7]}			Half-life ^[1]	Decay mode ^[1]	Daughter isotope ^{[n 4]}^{[n 5]}	Spin and parity ^[1] ^{[n 6]}^{[n 7]}	Isotopic abundance
¹⁸⁶Po		84	102	186.004403(20)	28+16 −6 μs	α	¹⁸²Pb	0+
¹⁸⁷Po		84	103	187.003030(40)	1.40(25) ms	α	¹⁸³Pb	1/2−, 5/2−
^187mPo^{[n 8]}		4(27) keV			0.5 ms	α	¹⁸³Pb	13/2+#
¹⁸⁸Po		84	104	187.999416(21)	270(30) μs	α	¹⁸⁴Pb	0+
¹⁸⁹Po		84	105	188.998473(24)	3.5(5) ms	α	¹⁸⁵Pb	(5/2−)
¹⁹⁰Po		84	106	189.995102(14)	2.45(5) ms	α	¹⁸⁶Pb	0+
¹⁹¹Po		84	107	190.994558(8)	22(1) ms	α	¹⁸⁷Pb	3/2−
^191mPo		61(11) keV			93(3) ms	α	^187mPb	13/2+
¹⁹²Po		84	108	191.991340(11)	32.2(3) ms	α	¹⁸⁸Pb	0+
^192mPo		2294.6(10) keV			580(100) ns	IT	¹⁹²Po	11−
¹⁹³Po		84	109	192.991062(16)	399(34) ms	α	¹⁸⁹Pb	3/2−
^193mPo		100(6) keV			245(11) ms	α	^189mPb	13/2+
¹⁹⁴Po		84	110	193.988186(14)	392(4) ms	α	¹⁹⁰Pb	0+
^194mPo		2313.4(3) keV			12.9(5) μs	IT	¹⁹⁴Po	(10−)
¹⁹⁵Po		84	111	194.988066(6)	4.64(9) s	α (94%)	¹⁹¹Pb	3/2−
¹⁹⁵Po		84	111	194.988066(6)	4.64(9) s	β⁺ (6%)	¹⁹⁵Bi	3/2−
^195mPo		148(9) keV			1.92(2) s	α	^191mPb	13/2+
¹⁹⁶Po		84	112	195.985541(6)	5.63(7) s	α (94%)	¹⁹²Pb	0+
¹⁹⁶Po		84	112	195.985541(6)	5.63(7) s	β⁺ (6%)	¹⁹⁶Bi	0+
^196mPo		2493.9(4) keV			856(17) ns	IT	¹⁹⁶Po	11−
¹⁹⁷Po		84	113	196.985622(11)	53.6(9) s	β⁺ (56%)	¹⁹⁷Bi	(3/2−)
¹⁹⁷Po		84	113	196.985622(11)	53.6(9) s	α (44%)	¹⁹³Pb	(3/2−)
^197mPo		196(12) keV			25.8(1) s	α (84%)	^193mPb	13/2+
						β⁺ ?	¹⁹⁷Bi
						IT ?	¹⁹⁷Po
¹⁹⁸Po		84	114	197.983389(19)	1.760(24) min	α (57%)	¹⁹⁴Pb	0+
¹⁹⁸Po		84	114	197.983389(19)	1.760(24) min	β⁺ (43%)	¹⁹⁸Bi	0+
^198m1Po		2565.92(20) keV			200(20) ns	IT	¹⁹⁸Po	11−
^198m2Po		2740(50)# keV			750(50) ns	IT	¹⁹⁸Po	12+
¹⁹⁹Po		84	115	198.983640(6)	5.47(15) min	β⁺ (92.5%)	¹⁹⁹Bi	3/2−
¹⁹⁹Po		84	115	198.983640(6)	5.47(15) min	α (7.5%)	¹⁹⁵Pb	3/2−
^199mPo		311.7(27) keV			4.17(5) min	β⁺ (73.5%)	¹⁹⁹Bi	13/2+
						α (24%)	¹⁹⁵Pb
						IT (2.5%)	¹⁹⁹Po
²⁰⁰Po		84	116	199.981812(8)	11.51(8) min	β⁺ (88.9%)	²⁰⁰Bi	0+
²⁰⁰Po		84	116	199.981812(8)	11.51(8) min	α (11.1%)	¹⁹⁶Pb	0+
^200m1Po		2596.1(3) keV			100(10) ns	IT	²⁰⁰Po	11-
^200m2Po		2817(7) keV			268(3) ns	IT	²⁰⁰Po	12+
²⁰¹Po		84	117	200.982264(5)	15.6(1) min	β⁺ (98.87%)	²⁰¹Bi	3/2−
²⁰¹Po		84	117	200.982264(5)	15.6(1) min	α (1.13%)	¹⁹⁷Pb	3/2−
^201mPo		423.8(24) keV			8.96(12) min	IT (56.2(12)%)	²⁰¹Po	13/2+
						β⁺ (41.4(7)%)	²⁰¹Bi
						α (2.4(5)%)	¹⁹⁷Pb
²⁰²Po		84	118	201.980739(9)	44.6(4) min	β⁺ (98.08%)	²⁰²Bi	0+
²⁰²Po		84	118	201.980739(9)	44.6(4) min	α (1.92%)	¹⁹⁸Pb	0+
^202mPo		1712(12) keV			110(15) ns	IT	²⁰²Po	8+
²⁰³Po		84	119	202.981416(5)	36.7(5) min	β⁺ (99.89%)	²⁰³Bi	5/2−
²⁰³Po		84	119	202.981416(5)	36.7(5) min	α (0.11%)	¹⁹⁹Pb	5/2−
^203m1Po		641.68(14) keV			45(2) s	IT	²⁰³Po	13/2+
^203m1Po		641.68(14) keV			45(2) s	α ?	¹⁹⁹Pb	13/2+
^203m2Po		2158.5(6) keV			>200 ns	IT	²⁰³Po
²⁰⁴Po		84	120	203.980310(11)	3.519(12) h	β⁺ (99.33%)	²⁰⁴Bi	0+
²⁰⁴Po		84	120	203.980310(11)	3.519(12) h	α (0.67%)	²⁰⁰Pb	0+
^204mPo		1639.03(6) keV			158.6(18) ns	IT	²⁰⁸Po	8+
²⁰⁵Po		84	121	204.981190(11)	1.74(8) h	β⁺ (99.96%)	²⁰⁵Bi	5/2−
²⁰⁵Po		84	121	204.981190(11)	1.74(8) h	α (0.04%)	²⁰¹Pb	5/2−
^205m1Po		143.166(15) keV			310(60) ns	IT	²⁰⁵Po	1/2−
^205m2Po		880.31(4) keV			645(20) μs	IT	²⁰⁵Po	13/2+
^205m3Po		1461.21(21) keV			57.4(9) ms	IT	²⁰⁵Po	19/2−
^205m4Po		3087.2(4) keV			115(10) ns	IT	²⁰⁵Po	29/2−
²⁰⁶Po		84	122	205.980474(4)	8.8(1) d	β⁺ (94.55%)	²⁰⁶Bi	0+
²⁰⁶Po		84	122	205.980474(4)	8.8(1) d	α (5.45%)	²⁰²Pb	0+
^206m1Po		1585.90(11) keV			232(4) ns	IT	²⁰⁶Po	8+
^206m2Po		2262.09(12) keV			1.05(6) μs	IT	²⁰⁶Po	9−
²⁰⁷Po		84	123	206.981593(7)	5.80(2) h	β⁺ (99.979%)	²⁰⁷Bi	5/2−
²⁰⁷Po		84	123	206.981593(7)	5.80(2) h	α (0.021%)	²⁰³Pb	5/2−
^207m1Po		68.557(14) keV			205(10) ns	IT	²⁰⁷Po	1/2−
^207m2Po		1115.076(17) keV			49(4) μs	IT	²⁰⁷Po	13/2+
^207m3Po		1383.16(7) keV			2.79(8) s	IT	²⁰⁷Po	19/2−
²⁰⁸Po		84	124	207.9812460(18)	2.898(2) y	α	²⁰⁴Pb	0+
²⁰⁸Po		84	124	207.9812460(18)	2.898(2) y	β⁺ (0.0042%)	²⁰⁸Bi	0+
^208mPo		1528.22(4) keV			373(8) ns	IT	²⁰⁸Po	8+
²⁰⁹Po		84	125	208.9824304(19)	124(3) y	α (99.546%)	²⁰⁵Pb	1/2−
²⁰⁹Po		84	125	208.9824304(19)	124(3) y	β⁺ (0.454%)	²⁰⁹Bi	1/2−
^209mPo		4265.4(3) keV			119(4) ns	IT	²⁰⁹Po	31/2−
²¹⁰Po ^{[n 9]}	Radium F	84	126	209.9828737(12)	138.376(2) d	α	²⁰⁶Pb	0+	Trace^{[n 10]}
^210m1Po		1556.97(3) keV			98.9(25) ns	IT	²¹⁰Po	8+
^210m2Po		5057.65(5) keV			263(5) ns	IT	²¹⁰Po	16+
²¹¹Po	Actinium C'	84	127	210.9866532(13)	516(3) ms	α	²⁰⁷Pb	9/2+	Trace^{[n 11]}
^211m1Po		1462(5) keV			25.2(6) s	α (99.984%)	²⁰⁷Pb	(25/2+)
^211m1Po		1462(5) keV			25.2(6) s	IT (0.016%)	²¹¹Po	(25/2+)
^211m2Po		2135(5) keV			243(21) ns	IT	²¹¹Po	(31/2−)
^211m3Po		4872(6) keV			2.8(7) μs	IT	²¹¹Po	(43/2+)
²¹²Po	Thorium C'	84	128	211.9888680(12)	294.4(8) ns	α	²⁰⁸Pb	0+	Trace^{[n 12]}
^212mPo		2923(4) keV			45.1(6) s	α (99.93%)	²⁰⁸Pb	(18+)
^212mPo		2923(4) keV			45.1(6) s	IT (0.07%)	²¹²Po	(18+)
²¹³Po		84	129	212.992857(3)	3.705(1) μs	α	²⁰⁹Pb	9/2+	Trace^{[n 13]}
²¹⁴Po	Radium C'	84	130	213.9952013(16)	163.47(3) μs	α	²¹⁰Pb	0+	Trace^{[n 10]}
²¹⁵Po	Actinium A	84	131	214.9994184(23)	1.781(5) ms	α	²¹¹Pb	9/2+	Trace^{[n 11]}
²¹⁵Po	Actinium A	84	131	214.9994184(23)	1.781(5) ms	β⁻ (2.3×10⁻⁴%)	²¹⁵At	9/2+	Trace^{[n 11]}
²¹⁶Po	Thorium A	84	132	216.0019134(19)	144.0(6) ms	α^{[n 14]}	²¹²Pb	0+	Trace^{[n 12]}
²¹⁷Po		84	133	217.006316(7)	1.53(5) s	α (97.5%)	²¹³Pb	(9/2+)	Trace^{[n 13]}
²¹⁷Po		84	133	217.006316(7)	1.53(5) s	β⁻ (2.5%)	²¹⁷At	(9/2+)	Trace^{[n 13]}
²¹⁸Po	Radium A	84	134	218.0089712(21)	3.097(12) min	α (99.98%)	²¹⁴Pb	0+	Trace^{[n 10]}
²¹⁸Po	Radium A	84	134	218.0089712(21)	3.097(12) min	β⁻ (0.02%)	²¹⁸At	0+	Trace^{[n 10]}
²¹⁹Po		84	135	219.013614(17)	10.3(10) min	β⁻ (71.8%)	²¹⁹At	9/2+#
²¹⁹Po		84	135	219.013614(17)	10.3(10) min	α (28.2%)	²¹⁵Pb	9/2+#
²²⁰Po		84	136	220.016386(19)	10# s [>300 ns]	β⁻ ?	²²⁰At	0+
²²¹Po		84	137	221.021228(21)	2.2 +/- 0.7 min	β⁻	²²¹At	9/2+#
²²²Po		84	138	222.02414(4)	9.1 +/- 7.2 min	β⁻	²²²At	0+
²²³Po		84	139	223.02907(21)#	6# s [>300 ns]	β⁻ ?	²²³At	11/2+#
²²⁴Po		84	140	224.03211(21)#	3# min [>300 ns]	β⁻ ?	²²⁴At	0+
²²⁵Po		84	141	225.03712(32)#	10# s [>300 ns]	β⁻ ?	²²⁵At	3/2+#
²²⁶Po		84	142	226.04031(43)#	1# min [>300 ns]	β⁻ ?	²²⁶At	0+
²²⁷Po		84	143	227.04539(43)#	2# s [>300 ns]	β⁻ ?	²²⁷At	5/2+#
This table header & footer: view

↑ ^mPo – 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).
↑ Bold italics symbol as daughter – Daughter product is nearly stable.
↑ Bold symbol as daughter – Daughter product is stable.
↑ ( ) spin value – Indicates spin with weak assignment arguments.
1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
↑ Order of ground state and isomer is uncertain.
↑ Most common isotope
1 2 3 Intermediate decay product of ²³⁸U
1 2 Intermediate decay product of ²³⁵U
1 2 Intermediate decay product of ²³²Th
1 2 Intermediate decay product of ²³⁷Np
↑ Theoretically capable of β⁻β⁻ decay to ²¹⁶Rn

Daughter products other than polonium

References

1 2 3 4 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.
↑ Carvalho, F.; Fernandes, S.; Fesenko, S.; Holm, E.; Howard, B.; Martin, P.; Phaneuf, P.; Porcelli, D.; Pröhl, G.; Twining, J. (2017). The Environmental Behaviour of Polonium. Technical reports series. Vol. 484. Vienna: International Atomic Energy Agency. p. 22. ISBN 978-92-0-112116-5. ISSN 0074-1914.
↑ 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.

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[3] Po – Excited nuclear isomer.

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

[TMS-6] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[7] Bold italics symbol as daughter – Daughter product is nearly stable.

[8] Bold symbol as daughter – Daughter product is stable.

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

[TNN-10] 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[11] Order of ground state and isomer is uncertain.

[12] Most common isotope

[rs-13] 1 2 3 Intermediate decay product of ²³⁸U

[as-14] 1 2 Intermediate decay product of ²³⁵U

[ths-15] 1 2 Intermediate decay product of ²³²Th

[ns-16] 1 2 Intermediate decay product of ²³⁷Np

[17] Theoretically capable of β⁻β⁻ decay to ²¹⁶Rn

[NUBASE2020-1] 1 2 3 4 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.

[po484-2] Carvalho, F.; Fernandes, S.; Fesenko, S.; Holm, E.; Howard, B.; Martin, P.; Phaneuf, P.; Porcelli, D.; Pröhl, G.; Twining, J. (2017). The Environmental Behaviour of Polonium. Technical reports series. Vol. 484. Vienna: International Atomic Energy Agency. p. 22. ISBN 978-92-0-112116-5. ISSN 0074-1914.

[AME2020_II-4] 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.

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