Isotopes of astatine

Astatine (₈₅At) has 41 known isotopes, all of which are radioactive, whose mass numbers range from 188 to 229 except 189; they are accompanied by almost as many metastable excited states. The longest-lived isotope is ²¹⁰At, which has a half-life of 8.1 hours, followed by the medically useful ²¹¹At, with a half-life of 7.214 hours. The longest-lived isomer is ^202m1At with a half-life of just over 3 minutes. However, the longest-lived isotope existing in naturally occurring decay chains is ²¹⁹At with a half-life of only 56 seconds.

Isotopes of astatine (₈₅At)

Main isotopes Decay Isotope abun­dance half-life (t1/2) mode pro­duct ^207At synth 1.81 h β^+90% ^207Po α10% ^203Bi ^208At synth 1.63 h β^+99.5% ^208Po α0.55% ^204Bi ^209At synth 5.41 h β^+96.1% ^209Po α3.9% ^205Bi ^210At synth 8.1 h β^+99.8% ^210Po α0.175% ^206Bi ^211At synth 7.214 h ε58.2% ^211Po α41.8% ^207Bi

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List of isotopes

Nuclide	Z	N	Isotopic mass (Da)	Half-life	Decay mode	Daughter isotope	Spin and parity	Isotopic abundance
	Excitation energy
^188At	85	103		190+350 −80 μs	α (~50%)	^184Bi
					p (~50%)	^187Po
^190At	85	105		1.0+1.4 −0.4 ms	α	^186Bi	(10−)
^191At	85	106	191.004148(17)	2.1(8) ms	α	^187Bi	1/2+
^191mAt	58(20) keV			2.2(4) ms	α	^187Bi	(7/2−)
^192At	85	107	192.003141(3)	11.5(6) ms	α	^188Bi	3+#
^192mAt	0(40) keV			88(6) ms	α	^188mBi	(9−, 10−)
^193At	85	108	192.999928(23)	29(5) ms	α	^189Bi	1/2+
^193m1At	8(9) keV			21(5) ms	α	^189m1Bi	7/2−
^193m2At	42(9) keV			28(4) ms	IT (76%)	^193At	13/2+
					α (24%)	^189m2Bi
^194At	85	109	193.999231(25)	286(7) ms	α (91.7%#)	^190Bi	(5−)
					β^+ (8.3%#)	^194Po
					β^+, SF (0.032%#)	(various)
^194mAt	−20(40) keV			323(7) ms	α (91.7%#)	^190Bi	10−
					β^+ (8.3%#)	^194Po
					β^+, SF (0.032%#)	(various)
^195At	85	110	194.996274(10)	290(20) ms	α	^191mBi	1/2+
					β^+ ?	^195Po
^195mAt	29(7) keV			143(3) ms	α (88%)	^191Bi	7/2-
					IT (12%)	^195At
					β^+?	^195Po
^196At	85	111	195.99580(3)	377(4) ms	α (97.5%)	^192Bi	(3+)
					β^+ (2.5%)	^196Po
					β^+, SF (0.009%)	(various)
^196m1At	−40(40) keV			20# ms	α	^192mBi	10−#
^196m2At	157.9(1) keV			11(2) μs	IT	^196At	(5+)
^197At	85	112	196.993177(9)	388.2(56) ms	α (96.1%)	^193Bi	9/2−
					β^+ (3.9%)	^197Po
^197m1At	45(8) keV			2.0(2) s	α	^193m1Bi	1/2+
					IT (<0.004%)	^197At
					β^+?	^197Po
^197m2At	310.7(2) keV			1.3(2) μs	IT	^197At	13/2+
^198At	85	113	197.992798(5)	4.47(5) s	α (97%)	^194Bi	3+
					β^+ (3%)	^198Po
^198mAt	266.6(27) keV			1.23(5) s	α (93%)		10−
					β^+ ?	^198Po
					IT ?	^198Po
^199At	85	114	198.990528(6)	7.02(12) s	α (89%)	^195Bi	9/2−
					β^+ (11%)	^199Po
^199m1At	244.0(10) keV			273(9) ms	IT (99%)		1/2+
					α (1%)	^195Bi
^199m2At	572.9(1) keV			70(20) ns	IT		13/2+
^199m3At	2293.4(5) keV			800(50) ns	IT		(29/2+)
^200At	85	115	199.990351(26)	43.2(9) s	α (52%)	^196Bi	(3+)
					β^+ (48%)	^200Po
^200m1At	112.9(29) keV			47(1) s	β^+ (57%)	^200Po	(7+)
					α (43%)	^196Bi
					IT ?	^200At
^200m2At	343.8(30) keV			8.0(21) s	IT ?	^200At	(10−)
					α (10.5%)	^196Bi
					β^+ ?	^200Po
^201At	85	116	200.988417(9)	85.2(16) s	α (71%)	^197Bi	9/2−
					β^+ (29%)	^201Po
^201m1At	459(1) keV			45(3) ms	IT		1/2+
^201m2At	459(1) keV			3.39(9) μs	IT		29/2+
^202At	85	117	201.988626(30)	184(1) s	β^+ (88%)	^202Po	3+
					α (12%)	^198Bi
^202m1At	190(40) keV			182(2) s	β^+ (91.5%)	^202Po	7+
					α (8.5%)	^198Bi
					IT ?	^202At
^202m2At	590(40) keV			460(50) ms	IT (99.904%)	^202At	10−
					α (0.096%)	^198Bi
					IT ?	^202At
^203At	85	118	202.986943(11)	7.4(2) min	β^+ (69%)	^203Po	9/2−
					α (31%)	^199Bi
^203m1At	683.4(3) keV			3.5(6) ms	IT		1/2+
^203m2At	2330.1(4) keV			9.77(21) μs	IT		29/2+
^204At	85	119	203.987251(24)	9.12(11) min	β^+ (96.2%)	^204Po	7+
					α (3.8%)	^200Bi
^204mAt	587.30(20) keV			108(10) ms	IT	^204At	10−
^205At	85	120	204.986061(13)	26.9(8) min	β^+ (90%)	^205Po	9/2−
					α (10%)	^201Bi
^205mAt	2339.64(23) keV			7.76(14) μs	IT	^205At	29/2+
^206At	85	121	205.986646(15)	30.6(8) min	β^+ (99.1%)	^206Po	(6)+
					α (0.9%)	^202Bi
^206mAt	810(2) keV			813(21) ns	IT	^206At	(10)−
^207At	85	122	206.985800(13)	1.81(3) h	β^+ (~90%)	^207Po	9/2−
					α (~10%)	^203Bi
^207mAt	2117.3(6) keV			108(2) ns	IT	^207At	25/2+
^208At	85	123	207.986613(10)	1.63(3) h	β^+ (99.45%)	^208Po	6+
					α (0.55%)	^204Bi
^208mAt	2276.4(18) keV			1.5(2) μs	IT	^208At	16-
^209At	85	124	208.986169(5)	5.42(5) h	β^+ (96.1%)	^209Po	9/2−
					α (3.9%)	^205Bi
^209mAt	2429.32(22) keV			916(10) ns	IT	^209At	29/2+
^210At	85	125	209.987147(8)	8.1(4) h	β^+ (99.825%)	^210Po	(5)+
					α (0.175%)	^206Bi
^210m1At	2549.6(2) keV			482(6) ns	IT	^210At	(15)−
^210m2At	4027.7(2) keV			5.66(7) μs	IT	^210At	(19)+
^211At	85	126	210.9874962(29)	7.214(7) h	EC (58.2%)	^211Po	9/2−
					α (41.8%)	^207Bi
^211mAt	4814.5(5) keV			4.23(7) μs	IT	^211At	(39/2-)
^212At	85	127	211.9907373(26)	314(3) ms	α	^208Bi	(1−)
^212m1At	222.9(9) keV			119(3) ms	α	^208Bi	(9−)
^212m2At	4771.4(15) keV			152(5) μs	IT	^212At	(25−)
^213At	85	128	212.992937(5)	125(6) ns	α	^209Bi	9/2−
^213m1At	1358(23) keV			110(17) ns	IT	^213At	25/2-#
^213m2At	2998(27) keV			45(4) μs	IT	^213At	49/2+#
^214At	85	129	213.996372(4)	558(10) ns	α	^210Bi	1−
^214m1At	59(9) keV			265(30) ns	α	^210Bi
^214m2At	232(5) keV			760(15) ns	α	^210mBi	9−
^215At	85	130	214.998651(7)	37(3) μs	α	^211Bi	9/2−	Trace
^216At	85	131	216.002423(4)	300(30) μs	α	^212Bi	1−
^216mAt	161(11) keV			100# μs	α	^212m1Bi	9−#
^217At	85	132	217.004718(5)	32.6(3) ms	α (99.992%)	^213Bi	9/2−	Trace
					β^− (0.008%)	^217Rn
^218At	85	133	218.008696(12)	1.28(6) s	α (~100%)	^214Bi	(2−,3−)	Trace
					β^− (?)	^218Rn
^219At	85	134	219.011161(3)	56(3) s	α (93.6%)	^215Bi	(9/2−)	Trace
					β^− (6.4%)	^219Rn
^220At	85	135	220.015433(15)	3.71(4) min	β^− (92%)	^220Rn	3(−#)
					α (8%)	^216Bi
^221At	85	136	221.018017(15)	2.3(2) min	β^−	^221Rn	3/2−#
^222At	85	137	222.022494(17)	54(10) s	β^−	^222Rn
^223At	85	138	223.025151(15)	50(7) s	β^−	^223Rn	3/2−#
^224At	85	139	224.029749(24)	2.5 +/- 1.5 min	β^−	^224Rn	2+#
^225At	85	140	225.03253(32)#	3# s (>300 ns)	β^− ?	^225Rn	1/2+#
^226At	85	141	226.03721(32)#	7# min (>300 ns)	β^− ?	^226Rn	2+#
^227At	85	142	227.04018(32)#	5# s (>300 ns)	β^− ?	^227Rn	1/2+#
^228At	85	143	228.04496(43)#	1# min (>300 ns)	β^− ?	^228Rn	3+#
^229At	85	144	229.04819(43)#	1# s (>300 ns)	β^− ?	^229Rn	1/2+#
This table header & footer: view

1. ^mAt – 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. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition

5. Bold italics symbol as daughter – Daughter product is nearly stable.
6. ( ) spin value – Indicates spin with weak assignment arguments.
7. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
8. Order of ground state and isomer is uncertain.
9. Theoretically capable of β⁺ decay to ²¹²Po or β⁻ decay to ²¹²Rn; the branching ratios are expected to be <3×10⁻²% and <2×10⁻⁶% (partial half-lives >17.4 min and >182 d) respectively.
10. Theoretically capable of electron capture to ²¹³Po; the branching ratio is expected to be <2.5×10⁻¹²% (partial half-life >57.9 d).
11. Intermediate decay product of ²³⁵U
12. Theoretically capable of electron capture to ²¹⁶Po or β⁻ decay to ²¹⁶Rn; the branching ratios are expected to be <3×10⁻⁷% and <6×10⁻³% (partial half-lives >1.2 d and >5.0 s) respectively.
13. Intermediate decay product of ²³⁷Np
14. Intermediate decay product of ²³⁸U

Alpha decay

Alpha decay characteristics for astatine isotopes, with all nuclear data from NUBASE2020.

Mass number	Mass excess	Mass excess of daughter	Energy of alpha decay	Half-life	Probability of alpha decay	Alpha decay half-life
195	−3.470 MeV	−10.814 MeV	7.344 MeV	0.29 s	~100%	0.29 s
196	−3.910 MeV	−11.105 MeV	7.195 MeV	0.377 s	97.5%	0.39 s
197	−6.355 MeV	−13.460 MeV	7.105 MeV	0.388 s	96.1%	0.40 s
198	−6.709 MeV	−13.598 MeV	6.889 MeV	4.47 s	97%	4.6 s
199	−8.823 MeV	−15.601 MeV	6.778 MeV	7.0 s	89%	7.9 s
200	−8.988 MeV	−15.584 MeV	6.596 MeV	43.2 s	52%	83 s
201	−10.789 MeV	−17.262 MeV	6.473 MeV	85.2 s	71%	2.0 min
202	−10.595 MeV	−16.949 MeV	6.354 MeV	184 s	12%	2.6 min
203	−12.163 MeV	−18.373 MeV	6.210 MeV	7.4 min	31%	2.4 min
204	−11.875 MeV	−17.946 MeV	6.071 MeV	9.1 min	3.8%	4.0 h
205	−12.985 MeV	−19.004 MeV	6.039 MeV	26.9 min	10%	4.5 h
206	−12.439 MeV	−18.326 MeV	5.887 MeV	30.6 min	0.90%	2.4 d
207	−13.227 MeV	−19.100 MeV	5.873 MeV	1.81 h	~10%	18 h
208	−12.470 MeV	−18.221 MeV	5.751 MeV	1.63 h	0.55%	12.3 d
209	−12.884 MeV	−18.641 MeV	5.757 MeV	5.42 h	3.9%	5.8 d
210	−11.972 MeV	−17.603 MeV	5.631 MeV	8.1 h	0.175%	193 d
211	−11.647 MeV	−17.630 MeV	5.983 MeV	7.214 h	41.80%	17 h
212	−8.628 MeV	−16.445 MeV	7.817 MeV	0.314 s	%	0.31 s
213	−6.580 MeV	−15.834 MeV	9.254 MeV	125 ns	100%	125 ns
214	−3.379 MeV	−12.367 MeV	8.988 MeV	0.56 μs	100%	0.56 μs
215	−1.257 MeV	−9.434 MeV	8.177 MeV	37 μs	100%	37 μs
216	2.257 MeV	−5.693 MeV	7.950 MeV	0.3 ms	100%	0.3 ms
217	4.395 MeV	−2.807 MeV	7.202 MeV	32.6 ms	99.992%	33 ms
218	8.100 MeV	1.224 MeV	6.876 MeV	1.28 s	~100%	1.28 s
219	10.396 MeV	4.054 MeV	6.342 MeV	56 s	93.6%	60 s
220	14.376 MeV	8.299 MeV	6.077 MeV	3.71 min	8%	46 min
221	16.783 MeV	11.155 MeV	5.628 MeV	2.3 min	experimentally alpha stable	-

Alpha decay energy follows the same trend as for other heavy elements. The lighter astatine isotopes have quite high decay energies, which become lower as more neutrons are added, reaching a minimum at 125 neutrons (astatine-210), even though 126 (astatine-211) is the magic number. The decay energies increase much more steeply, though, on the next two steps, reaching a high at 128 neutrons where the alpha-decay product would have the magic number of 126. Here this is astatine-213, releasing the highest energy and having the shortest life (125 ns) of all the isotopes. The energy then declines again, and alpha lifetimes increase quickly, no long-lived astatine isotope exists; this happens due to the increasing role of beta decay. This decay mode is especially important for astatine: as early as 1950, it was postulated that the element has no beta-stable isotopes (i.e. ones that do not undergo beta decay at all), though nuclear mass measurements reveal that ²¹⁵At is in fact beta-stable, as it has the lowest mass of all isobars with A = 215. A beta decay mode has been found for all other astatine isotopes except for ^212-216At and their isomers. Among other isotopes, if they do not undergo alpha decay: astatine-210 and the lighter isotopes decay by electron capture or positron emission, 211 by electron capture only, and astatine-217 and heavier isotopes undergo β^- decay. Astatine-212, 214, and 216 should be able to decay either way.

See also

Daughter products other than astatine

• Isotopes of radon
• Isotopes of polonium
• Isotopes of bismuth

Notes

1. In the table, under the words "mass excess", the energy equivalents are given rather than the real mass excesses; "mass excess of daughter" stands for the energy equivalent of the mass excess sum of the daughter of the isotope and the alpha particle; "alpha decay half-life" refers to the half-life if decay modes other than alpha are omitted.

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