Isotopes of actinium

Isotopes of actinium (89Ac)
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
225Ac trace 9.919 d α 221Fr
14C 211Bi
226Ac synth 29.37 h β 226Th
ε 226Ra
α 222Fr
227Ac trace 21.772 y β 227Th
α 223Fr

Actinium (89Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 34 known isotopes, from 203Ac to 236Ac, and 7 isomers. Three isotopes are found in nature, 225Ac, 227Ac and 228Ac, as intermediate decay products of, respectively, 237Np, 235U, and 232Th. 228Ac and 225Ac are extremely rare, so almost all natural actinium is 227Ac.

The most stable isotopes are 227Ac with a half-life of 21.772 years, 225Ac with a half-life of 10.0 days, and 226Ac with a half-life of 29.37 hours. All other isotopes have half-lives under 10 hours, and most under a minute. The shortest-lived known isotope is 217Ac with a half-life of 69 ns.

Purified 227Ac comes into equilibrium with its decay products (227Th and 223Fr) after 185 days.

List of isotopes

Nuclide
Historic
name
Z N Isotopic mass (Da)
Half-life
Decay
mode

Daughter
isotope

Spin and
parity
Isotopic
abundance
Excitation energy
203Ac 89 114 56+269
−26
 μs
α 199Fr (1/2+)
204Ac 89 115 7.4+2.2
−1.4
 ms
α 200Fr
205Ac 89 116 7.7+2.7
−1.6
 ms
α 201Fr 9/2−?
206Ac 89 117 206.01450(8) 25(7) ms α 202Fr (3+)
206m1Ac 80(50) keV 15(6) ms α 202Fr
206m2Ac 290(110)# keV 41(16) ms α 202mFr (10−)
207Ac 89 118 207.01195(6) 31(8) ms
[27(+11−6) ms]
α 203Fr 9/2−#
208Ac 89 119 208.01155(6) 97(16) ms
[95(+24−16) ms]
α (99%) 204Fr (3+)
β+ (1%) 208Ra
208mAc 506(26) keV 28(7) ms
[25(+9−5) ms]
α (89%) 204Fr (10−)
IT (10%) 208Ac
β+ (1%) 208Ra
209Ac 89 120 209.00949(5) 92(11) ms α (99%) 205Fr (9/2−)
β+ (1%) 209Ra
210Ac 89 121 210.00944(6) 350(40) ms α (96%) 206Fr 7+#
β+ (4%) 210Ra
211Ac 89 122 211.00773(8) 213(25) ms α (99.8%) 207Fr 9/2−#
β+ (.2%) 211Ra
212Ac 89 123 212.00781(7) 920(50) ms α (97%) 208Fr 6+#
β+ (3%) 212Ra
213Ac 89 124 213.00661(6) 731(17) ms α 209Fr (9/2−)#
β+ (rare) 213Ra
214Ac 89 125 214.006902(24) 8.2(2) s α (89%) 210Fr (5+)#
β+ (11%) 214Ra
215Ac 89 126 215.006454(23) 0.17(1) s α (99.91%) 211Fr 9/2−
β+ (.09%) 215Ra
216Ac 89 127 216.008720(29) 0.440(16) ms α 212Fr (1−)
β+ (7×10−5%) 216Ra
216mAc 44(7) keV 443(7) µs α 212Fr (9−)
217Ac 89 128 217.009347(14) 69(4) ns α 213Fr 9/2−
β+ (6.9×10−9%) 217Ra
217mAc 2012(20) keV 740(40) ns (29/2)+
218Ac 89 129 218.01164(5) 1.08(9) µs α 214Fr (1−)#
218mAc 584(50)# keV 103(11) ns (11+)
219Ac 89 130 219.01242(5) 11.8(15) µs α 215Fr 9/2−
β+ (10−6%) 219Ra
220Ac 89 131 220.014763(16) 26.36(19) ms α 216Fr (3−)
β+ (5×10−4%) 220Ra
221Ac 89 132 221.01559(5) 52(2) ms α 217Fr 9/2−#
222Ac 89 133 222.017844(6) 5.0(5) s α (99%) 218Fr 1−
β+ (1%) 222Ra
222mAc 200(150)# keV 1.05(7) min α (88.6%) 218Fr high
IT (10%) 222Ac
β+ (1.4%) 222Ra
223Ac 89 134 223.019137(8) 2.10(5) min α (99%) 219Fr (5/2−)
EC (1%) 223Ra
CD (3.2×10−9%) 209Bi
14C
224Ac 89 135 224.021723(4) 2.78(17) h β+ (90.9%) 224Ra 0−
α (9.1%) 220Fr
β (1.6%) 224Th
225Ac 89 136 225.023230(5) 10.0(1) d α 221Fr (3/2−) Trace
CD (6×10−10%) 211Bi
14C
226Ac 89 137 226.026098(4) 29.37(12) h β (83%) 226Th (1)(−#)
EC (17%) 226Ra
α (.006%) 222Fr
227Ac Actinium 89 138 227.0277521(26) 21.772(3) y β (98.62%) 227Th 3/2− Trace
α (1.38%) 223Fr
228Ac Mesothorium 2 89 139 228.0310211(27) 6.13(2) h β 228Th 3+ Trace
229Ac 89 140 229.03302(4) 62.7(5) min β 229Th (3/2+)
230Ac 89 141 230.03629(32) 122(3) s β 230Th (1+)
231Ac 89 142 231.03856(11) 7.5(1) min β 231Th (1/2+)
232Ac 89 143 232.04203(11) 119(5) s β 232Th (1+)
233Ac 89 144 233.04455(32)# 145(10) s β 233Th (1/2+)
234Ac 89 145 234.04842(43)# 44(7) s β 234Th
235Ac 89 146 235.05123(38)# 60(4) s β 235Th 1/2+#
236Ac 89 147 236.05530(54)# 72+345
−33
 s
β 236Th
This table header & footer:
  1. ^ mAc – 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:
    CD: Cluster 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. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  8. ^ Has medical uses
  9. ^ Intermediate decay product of 237Np
  10. ^ Source of element's name
  11. ^ Intermediate decay product of 235U
  12. ^ Intermediate decay product of 232Th

Actinides vs fission products

Actinides by decay chain Half-life
range (a)
Fission products of 235U by yield
4n 4n + 1 4n + 2 4n + 3 4.5–7% 0.04–1.25% <0.001%
228Ra 4–6 a 155Euþ
244Cmƒ 241Puƒ 250Cf 227Ac 10–29 a 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ 243Cmƒ 29–97 a 137Cs 151Smþ 121mSn
248Bk 249Cfƒ 242mAmƒ 141–351 a

No fission products have a half-life
in the range of 100 a–210 ka ...

241Amƒ 251Cfƒ 430–900 a
226Ra 247Bk 1.3–1.6 ka
240Pu 229Th 246Cmƒ 243Amƒ 4.7–7.4 ka
245Cmƒ 250Cm 8.3–8.5 ka
239Puƒ 24.1 ka
230Th 231Pa 32–76 ka
236Npƒ 233Uƒ 234U 150–250 ka 99Tc 126Sn
248Cm 242Pu 327–375 ka 79Se
1.53 Ma 93Zr
237Npƒ 2.1–6.5 Ma 135Cs 107Pd
236U 247Cmƒ 15–24 Ma 129I
244Pu 80 Ma

... nor beyond 15.7 Ma

232Th 238U 235Uƒ№ 0.7–14.1 Ga

See also


This page was last updated at 2024-04-19 08:40 UTC. Update now. View original page.

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