Actinium (Ac) has no stable isotopes. A standard atomic mass cannot be given.
Additional recommended knowledge
An isotope of actinium occurring within the radioactive disintegration chain of thorium was known as:
The older name of emanium is no longer in use.
Naturally occurring actinium is composed of 1 radioactive isotope; 227Ac. 36 radioisotopes have been characterized with the most stable being 227Ac with a half-life of 21.772 y, 225Ac with a half-life of 10.0 days, and 226Ac with a half-life of 29.37 h. 227Ac
decays to Francium (223Fr) through alpha decay[1] or
Thorium (227Th) through beta decay.
All of the remaining radioactive isotopes have half-lifes that are less than 10 hours and the majority of these have half lifes that are less than 1 minute. The shortest-lived isotope of actinium is 217Ac which decays through alpha decay and electron capture. It has a half-life of 69 ns. Actinium also has 2 meta states.
Purified 227Ac comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.773-year half-life.
The isotopes of actinium range in atomic weight from 206 u (206Ac) to 236 u (236Ac).
Table
nuclide symbol
| Z(p)
| N(n)
| isotopic mass (u)
| half-life
| nuclear spin
| representative isotopic composition (mole fraction)
| range of natural variation (mole fraction)
|
excitation energy
|
206Ac
| 89
| 117
| 206.01450(8)
| 25(7) ms
| (3+)
|
|
|
206m1Ac
| 80(50) keV
| 15(6) ms
|
|
|
|
206m2Ac
| 290(110)# keV
| 41(16) ms
| (10-)
|
|
|
207Ac
| 89
| 118
| 207.01195(6)
| 31(8) ms [27(+11-6) ms]
| 9/2-#
|
|
|
208Ac
| 89
| 119
| 208.01155(6)
| 97(16) ms [95(+24-16) ms]
| (3+)
|
|
|
208mAc
| 506(26) keV
| 28(7) ms [25(+9-5) ms]
| (10-)
|
|
|
209Ac
| 89
| 120
| 209.00949(5)
| 92(11) ms
| (9/2-)
|
|
|
210Ac
| 89
| 121
| 210.00944(6)
| 350(40) ms
| 7+#
|
|
|
211Ac
| 89
| 122
| 211.00773(8)
| 213(25) ms
| 9/2-#
|
|
|
212Ac
| 89
| 123
| 212.00781(7)
| 920(50) ms
| 6+#
|
|
|
213Ac
| 89
| 124
| 213.00661(6)
| 731(17) ms
| (9/2-)#
|
|
|
214Ac
| 89
| 125
| 214.006902(24)
| 8.2(2) s
| (5+)#
|
|
|
215Ac
| 89
| 126
| 215.006454(23)
| 0.17(1) s
| 9/2-
|
|
|
216Ac
| 89
| 127
| 216.008720(29)
| 0.440(16) ms
| (1-)
|
|
|
216mAc
| 44(7) keV
| 443(7) µs
| (9-)
|
|
|
217Ac
| 89
| 128
| 217.009347(14)
| 69(4) ns
| 9/2-
|
|
|
217mAc
| 2012(20) keV
| 740(40) ns
| (29/2)+
|
|
|
218Ac
| 89
| 129
| 218.01164(5)
| 1.08(9) µs
| (1-)#
|
|
|
218mAc
| 584(50)# keV
| 103(11) ns
| (11+)
|
|
|
219Ac
| 89
| 130
| 219.01242(5)
| 11.8(15) µs
| 9/2-
|
|
|
220Ac
| 89
| 131
| 220.014763(16)
| 26.36(19) ms
| (3-)
|
|
|
221Ac
| 89
| 132
| 221.01559(5)
| 52(2) ms
| 9/2-#
|
|
|
222Ac
| 89
| 133
| 222.017844(6)
| 5.0(5) s
| 1-
|
|
|
222mAc
| 200(150)# keV
| 1.05(7) min
| high
|
|
|
223Ac
| 89
| 134
| 223.019137(8)
| 2.10(5) min
| (5/2-)
|
|
|
224Ac
| 89
| 135
| 224.021723(4)
| 2.78(17) h
| 0-
|
|
|
225Ac
| 89
| 136
| 225.023230(5)
| 10.0(1) d
| (3/2-)
|
|
|
226Ac
| 89
| 137
| 226.026098(4)
| 29.37(12) h
| (1)(-#)
|
|
|
227Ac
| 89
| 138
| 227.0277521(26)
| 21.772(3) a
| 3/2-
|
|
|
228Ac
| 89
| 139
| 228.0310211(27)
| 6.15(2) h
| 3+
|
|
|
229Ac
| 89
| 140
| 229.03302(4)
| 62.7(5) min
| (3/2+)
|
|
|
230Ac
| 89
| 141
| 230.03629(32)
| 122(3) s
| (1+)
|
|
|
231Ac
| 89
| 142
| 231.03856(11)
| 7.5(1) min
| (1/2+)
|
|
|
232Ac
| 89
| 143
| 232.04203(11)
| 119(5) s
| (1+)
|
|
|
233Ac
| 89
| 144
| 233.04455(32)#
| 145(10) s
| (1/2+)
|
|
|
234Ac
| 89
| 145
| 234.04842(43)#
| 44(7) s
|
|
|
|
235Ac
| 89
| 146
| 235.05123(38)#
| 40# s
| 1/2+#
|
|
|
236Ac
| 89
| 147
| 236.05530(54)#
| 2# min
|
|
|
|
Notes
- Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
- Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.
References
- ^ Considine, Glenn D., ed. (2005), , , New York: Wylie-Interscience, pp. 332, 0-471-61525-0
- Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
- National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
- David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
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