Actinium Actinium is a chemical element with the symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name ''emanium''; the element got its name by being wrongly identified with a substance And ...

(₈₉Ac) has no stable

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

s and no characteristic terrestrial isotopic composition, thus a

standard atomic weight The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, is ...

cannot be given. There are 33 known isotopes, from ²⁰⁴Ac to ²³⁶Ac, and 7

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

. 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

, - , ²⁰⁴Ac , , style="text-align:right" , 89 , style="text-align:right" , 115 , , , α , ²⁰⁰Fr , , , - , ²⁰⁵Ac , , style="text-align:right" , 89 , style="text-align:right" , 116 , , , α , ²⁰¹Fr , 9/2−? , , - , ²⁰⁶Ac , , style="text-align:right" , 89 , style="text-align:right" , 117 , 206.01450(8) , 25(7) ms , α , ²⁰²Fr , (3+) , , - , style="text-indent:1em" , ^206m1Ac , , colspan="3" style="text-indent:2em" , 80(50) keV , 15(6) ms , α , ²⁰²Fr , , , - , style="text-indent:1em" , ^206m2Ac , , colspan="3" style="text-indent:2em" , 290(110)# keV , 41(16) ms , α , ^202mFr , (10−) , , - , ²⁰⁷Ac , , style="text-align:right" , 89 , style="text-align:right" , 118 , 207.01195(6) , 31(8) ms
7(+11−6) ms, α , ²⁰³Fr , 9/2−# , , - , rowspan=2, ²⁰⁸Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 119 , rowspan=2, 208.01155(6) , rowspan=2, 97(16) ms
5(+24−16) ms, α (99%) , ²⁰⁴Fr , rowspan=2, (3+) , rowspan=2, , - , β⁺ (1%) , ²⁰⁸Ra , - , rowspan=3 style="text-indent:1em" , ^208mAc , rowspan=3, , rowspan=3 colspan="3" style="text-indent:2em" , 506(26) keV , rowspan=3, 28(7) ms
5(+9−5) ms, α (89%) , ²⁰⁴Fr , rowspan=3, (10−) , rowspan=3, , - , IT (10%) , ²⁰⁸Ac , - , β⁺ (1%) , ²⁰⁸Ra , - , rowspan=2, ²⁰⁹Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 120 , rowspan=2, 209.00949(5) , rowspan=2, 92(11) ms , α (99%) , ²⁰⁵Fr , rowspan=2, (9/2−) , rowspan=2, , - , β⁺ (1%) , ²⁰⁹Ra , - , rowspan=2, ²¹⁰Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 121 , rowspan=2, 210.00944(6) , rowspan=2, 350(40) ms , α (96%) , ²⁰⁶Fr , rowspan=2, 7+# , rowspan=2, , - , β⁺ (4%) , ²¹⁰Ra , - , rowspan=2, ²¹¹Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 122 , rowspan=2, 211.00773(8) , rowspan=2, 213(25) ms , α (99.8%) , ²⁰⁷Fr , rowspan=2, 9/2−# , rowspan=2, , - , β⁺ (.2%) , ²¹¹Ra , - , rowspan=2, ²¹²Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 123 , rowspan=2, 212.00781(7) , rowspan=2, 920(50) ms , α (97%) , ²⁰⁸Fr , rowspan=2, 6+# , rowspan=2, , - , β⁺ (3%) , ²¹²Ra , - , rowspan=2, ²¹³Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 124 , rowspan=2, 213.00661(6) , rowspan=2, 731(17) ms , α , ²⁰⁹Fr , rowspan=2, (9/2−)# , rowspan=2, , - , β⁺ (rare) , ²¹³Ra , - , rowspan=2, ²¹⁴Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 125 , rowspan=2, 214.006902(24) , rowspan=2, 8.2(2) s , α (89%) , ²¹⁰Fr , rowspan=2, (5+)# , rowspan=2, , - , β⁺ (11%) , ²¹⁴Ra , - , rowspan=2, ²¹⁵Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 126 , rowspan=2, 215.006454(23) , rowspan=2, 0.17(1) s , α (99.91%) , ²¹¹Fr , rowspan=2, 9/2− , rowspan=2, , - , β⁺ (.09%) , ²¹⁵Ra , - , rowspan=2, ²¹⁶Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 127 , rowspan=2, 216.008720(29) , rowspan=2, 0.440(16) ms , α , ²¹²Fr , rowspan=2, (1−) , rowspan=2, , - , β⁺ (7×10⁻⁵%) , ²¹⁶Ra , - , style="text-indent:1em" , ^216mAc , , colspan="3" style="text-indent:2em" , 44(7) keV , 443(7) µs , , , (9−) , , - , rowspan=2, ²¹⁷Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 128 , rowspan=2, 217.009347(14) , rowspan=2, 69(4) ns , α (98%) , ²¹³Fr , rowspan=2, 9/2− , rowspan=2, , - , β⁺ (6.9×10⁻⁹%) , ²¹⁷Ra , - , style="text-indent:1em" , ^217mAc , , colspan="3" style="text-indent:2em" , 2012(20) keV , 740(40) ns , , , (29/2)+ , , - , ²¹⁸Ac , , style="text-align:right" , 89 , style="text-align:right" , 129 , 218.01164(5) , 1.08(9) µs , α , ²¹⁴Fr , (1−)# , , - , style="text-indent:1em" , ^218mAc , , colspan="3" style="text-indent:2em" , 584(50)# keV , 103(11) ns , , , (11+) , , - , rowspan=2, ²¹⁹Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 130 , rowspan=2, 219.01242(5) , rowspan=2, 11.8(15) µs , α , ²¹⁵Fr , rowspan=2, 9/2− , rowspan=2, , - , β⁺ (10⁻⁶%) , ²¹⁹Ra , - , rowspan=2, ²²⁰Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 131 , rowspan=2, 220.014763(16) , rowspan=2, 26.36(19) ms , α , ²¹⁶Fr , rowspan=2, (3−) , rowspan=2, , - , β⁺ (5×10⁻⁴%) , ²²⁰Ra , - , ²²¹Ac , , style="text-align:right" , 89 , style="text-align:right" , 132 , 221.01559(5) , 52(2) ms , α , ²¹⁷Fr , 9/2−# , , - , rowspan=2, ²²²Ac , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 133 , rowspan=2, 222.017844(6) , rowspan=2, 5.0(5) s , α (99%) , ²¹⁸Fr , rowspan=2, 1− , rowspan=2, , - , β⁺ (1%) , ²²²Ra , - , rowspan=3 style="text-indent:1em" , ^222mAc , rowspan=3, , rowspan=3 colspan="3" style="text-indent:2em" , 200(150)# keV , rowspan=3, 1.05(7) min , α (88.6%) , ²¹⁸Fr , rowspan=3, high , rowspan=3, , - , IT (10%) , ²²²Ac , - , β⁺ (1.4%) , ²²²Ra , - , rowspan=3, ²²³Ac , rowspan=3, , rowspan=3 style="text-align:right" , 89 , rowspan=3 style="text-align:right" , 134 , rowspan=3, 223.019137(8) , rowspan=3, 2.10(5) min , α (99%) , ²¹⁹Fr , rowspan=3, (5/2−) , rowspan=3, , - , EC (1%) , ²²³Ra , - , CD (3.2×10⁻⁹%) , ''²⁰⁹Bi''
¹⁴C , - , rowspan=3, ²²⁴Ac , rowspan=3, , rowspan=3 style="text-align:right" , 89 , rowspan=3 style="text-align:right" , 135 , rowspan=3, 224.021723(4) , rowspan=3, 2.78(17) h , β⁺ (90.9%) , ²²⁴Ra , rowspan=3, 0− , rowspan=3, , - , α (9.1%) , ²²⁰Fr , - , β⁻ (1.6%) , ²²⁴Th , - , rowspan=2, ²²⁵AcHas medical uses , rowspan=2, , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 136 , rowspan=2, 225.023230(5) , rowspan=2, 10.0(1) d , α , ²²¹Fr , rowspan=2, (3/2−) , rowspan=2, TraceIntermediate decay product of ²³⁷Np , - , CD (6×10⁻¹⁰%) , ²¹¹Bi
¹⁴C , - , rowspan=3, ²²⁶Ac , rowspan=3, , rowspan=3 style="text-align:right" , 89 , rowspan=3 style="text-align:right" , 137 , rowspan=3, 226.026098(4) , rowspan=3, 29.37(12) h , β⁻ (83%) , ²²⁶Th , rowspan=3, (1)(−#) , rowspan=3, , - , EC (17%) , ²²⁶Ra , - , α (.006%) , ²²²Fr , - , rowspan=2, ²²⁷Ac , rowspan=2, ActiniumSource of element's name , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 138 , rowspan=2, 227.0277521(26) , rowspan=2, 21.772(3) y , β⁻ (98.61%) , ²²⁷Th , rowspan=2, 3/2− , rowspan=2, TraceIntermediate

decay product In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( ...

of ²³⁵U , - , α (1.38%) , ²²³Fr , - , rowspan=2, ²²⁸Ac , rowspan=2, Mesothorium 2 , rowspan=2 style="text-align:right" , 89 , rowspan=2 style="text-align:right" , 139 , rowspan=2, 228.0310211(27) , rowspan=2, 6.13(2) h , β⁻ , ²²⁸Th , rowspan=2, 3+ , rowspan=2, TraceIntermediate decay product of ²³²Th , - , α (5.5×10⁻⁶%) , ²²⁴Fr , - , ²²⁹Ac , , style="text-align:right" , 89 , style="text-align:right" , 140 , 229.03302(4) , 62.7(5) min , β⁻ , ²²⁹Th , (3/2+) , , - , ²³⁰Ac , , style="text-align:right" , 89 , style="text-align:right" , 141 , 230.03629(32) , 122(3) s , β⁻ , ²³⁰Th , (1+) , , - , ²³¹Ac , , style="text-align:right" , 89 , style="text-align:right" , 142 , 231.03856(11) , 7.5(1) min , β⁻ , ²³¹Th , (1/2+) , , - , ²³²Ac , , style="text-align:right" , 89 , style="text-align:right" , 143 , 232.04203(11) , 119(5) s , β⁻ , ''²³²Th'' , (1+) , , - , ²³³Ac , , style="text-align:right" , 89 , style="text-align:right" , 144 , 233.04455(32)# , 145(10) s , β⁻ , ²³³Th , (1/2+) , , - , ²³⁴Ac , , style="text-align:right" , 89 , style="text-align:right" , 145 , 234.04842(43)# , 44(7) s , β⁻ , ²³⁴Th , , , - , ²³⁵Ac , , style="text-align:right" , 89 , style="text-align:right" , 146 , 235.05123(38)# , 60(4) s , β⁻ , ²³⁵Th , 1/2+# , , - , ²³⁶Ac , , style="text-align:right" , 89 , style="text-align:right" , 147 , 236.05530(54)# , , β⁻ , ²³⁶Th , ,

Actinides vs fission products

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Authority control Actinium

List of isotopes

Actinides vs fission products

See also

References