Naturally occurring

terbium Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with w ...

(₆₅Tb) is composed of one 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 numb ...

, ¹⁵⁹Tb. Thirty-seven

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s have been characterized, with the most stable being ¹⁵⁸Tb with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

of 180 years, ¹⁵⁷Tb with a half-life of 71 years, and ¹⁶⁰Tb with a half-life of 72.3 days. All of the remaining

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

isotopes have half-lives that are less than 6.907 days, and the majority of these have half-lives that are less than 24 seconds. This element also has 27

meta state A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...

s, with the most stable being ^156m1Tb (t_1/2 = 24.4 hours), ^154m2Tb (t_1/2 = 22.7 hours) and ^154m1Tb (t_1/2 = 9.4 hours). The primary decay mode before the most abundant stable isotope, ¹⁵⁹Tb, is

electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...

, and the primary mode behind is

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...

. The primary decay products before ¹⁵⁹Tb are element Gd (

gadolinium Gadolinium is a chemical element with the symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with atmospheric oxygen ...

) isotopes, and the primary products after ¹⁵⁹Tb are element Dy (

dysprosium Dysprosium is the chemical element with the symbol Dy and atomic number 66. It is a rare-earth element in the lanthanide series with a metallic silver luster. Dysprosium is never found in nature as a free element, though, like other lanthanides, ...

) isotopes.

List of isotopes

, - , ¹³⁵Tb , style="text-align:right" , 65 , style="text-align:right" , 70 , , 0.94(+33−22) ms , , , (7/2−) , , , - , ¹³⁶Tb , style="text-align:right" , 65 , style="text-align:right" , 71 , 135.96138(64)# , 0.2# s , , , , , , - , ¹³⁷Tb , style="text-align:right" , 65 , style="text-align:right" , 72 , 136.95598(64)# , 600# ms , , , 11/2−# , , , - , rowspan=2, ¹³⁸Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 73 , rowspan=2, 137.95316(43)# , rowspan=2, 800# ms 200 ns, β⁺ , ¹³⁸Gd , rowspan=2, , rowspan=2, , rowspan=2, , - , p , ¹³⁷Gd , - , ¹³⁹Tb , style="text-align:right" , 65 , style="text-align:right" , 74 , 138.94829(32)# , 1.6(2) s , β⁺ , ¹³⁹Gd , 11/2−# , , , - , rowspan=2, ¹⁴⁰Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 75 , rowspan=2, 139.94581(86) , rowspan=2, 2.4(2) s , β⁺ (99.74%) , ¹⁴⁰Gd , rowspan=2, 5 , rowspan=2, , rowspan=2, , - , β⁺, p (.26%) , ¹³⁹Eu , - , ¹⁴¹Tb , style="text-align:right" , 65 , style="text-align:right" , 76 , 140.94145(11) , 3.5(2) s , β⁺ , ¹⁴¹Gd , (5/2−) , , , - , style="text-indent:1em" , ^141mTb , colspan="3" style="text-indent:2em" , 0(200)# keV , 7.9(6) s , β⁺ , ¹⁴¹Gd , 11/2−# , , , - , rowspan=2, ¹⁴²Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 77 , rowspan=2, 141.93874(32)# , rowspan=2, 597(17) ms , β⁺ , ¹⁴²Gd , rowspan=2, 1+ , rowspan=2, , rowspan=2, , - , β⁺, p , ¹⁴¹Eu , - , rowspan=2 style="text-indent:1em" , ^142m1Tb , rowspan=2 colspan="3" style="text-indent:2em" , 280.2(10) keV , rowspan=2, 303(17) ms , IT (99.5%) , ¹⁴²Tb , rowspan=2, (5−) , rowspan=2, , rowspan=2, , - , β⁺ (.5%) , ¹⁴²Gd , - , style="text-indent:1em" , ^142m2Tb , colspan="3" style="text-indent:2em" , 621.4(11) keV , 15(4) µs , , , , , , - , ¹⁴³Tb , style="text-align:right" , 65 , style="text-align:right" , 78 , 142.93512(6) , 12(1) s , β⁺ , ¹⁴³Gd , (11/2−) , , , - , style="text-indent:1em" , ^143mTb , colspan="3" style="text-indent:2em" , 0(100)# keV , <21 s , β⁺ , ¹⁴³Gd , 5/2+# , , , - , rowspan=2, ¹⁴⁴Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 79 , rowspan=2, 143.93305(3) , rowspan=2, ~1 s , β⁺ , ¹⁴⁴Gd , rowspan=2, 1+ , rowspan=2, , rowspan=2, , - , β⁺, p (rare) , ¹⁴³Eu , - , rowspan=3 style="text-indent:1em" , ^144m1Tb , rowspan=3 colspan="3" style="text-indent:2em" , 396.9(5) keV , rowspan=3, 4.25(15) s , IT (66%) , ¹⁴⁴Tb , rowspan=3, (6−) , rowspan=3, , rowspan=3, , - , β⁺ (34%) , ¹⁴⁴Gd , - , β⁺, p (<1%) , ¹⁴³Eu , - , style="text-indent:1em" , ^144m2Tb , colspan="3" style="text-indent:2em" , 476.2(5) keV , 2.8(3) µs , , , (8−) , , , - , style="text-indent:1em" , ^144m3Tb , colspan="3" style="text-indent:2em" , 517.1(5) keV , 670(60) ns , , , (9+) , , , - , style="text-indent:1em" , ^144m4Tb , colspan="3" style="text-indent:2em" , 544.5(6) keV , <300 ns , , , (10+) , , , - , ¹⁴⁵Tb , style="text-align:right" , 65 , style="text-align:right" , 80 , 144.92927(6) , 20# min , β⁺ , ¹⁴⁵Gd , (3/2+) , , , - , style="text-indent:1em" , ^145mTb , colspan="3" style="text-indent:2em" , 0(100)# keV , 30.9(7) s , β⁺ , ¹⁴⁵Gd , (11/2−) , , , - , ¹⁴⁶Tb , style="text-align:right" , 65 , style="text-align:right" , 81 , 145.92725(5) , 8(4) s , β⁺ , ¹⁴⁶Gd , 1+ , , , - , style="text-indent:1em" , ^146m1Tb , colspan="3" style="text-indent:2em" , 150(100)# keV , 24.1(5) s , β⁺ , ¹⁴⁶Gd , 5− , , , - , style="text-indent:1em" , ^146m2Tb , colspan="3" style="text-indent:2em" , 930(100)# keV , 1.18(2) ms , , , (10+) , , , - , ¹⁴⁷Tb , style="text-align:right" , 65 , style="text-align:right" , 82 , 146.924045(13) , 1.64(3) h , β⁺ , ¹⁴⁷Gd , 1/2+# , , , - , style="text-indent:1em" , ^147mTb , colspan="3" style="text-indent:2em" , 50.6(9) keV , 1.87(5) min , β⁺ , ¹⁴⁷Gd , (11/2)− , , , - , ¹⁴⁸Tb , style="text-align:right" , 65 , style="text-align:right" , 83 , 147.924272(15) , 60(1) min , β⁺ , ¹⁴⁸Gd , 2− , , , - , style="text-indent:1em" , ^148m1Tb , colspan="3" style="text-indent:2em" , 90.1(3) keV , 2.20(5) min , β⁺ , ¹⁴⁸Gd , (9)+ , , , - , style="text-indent:1em" , ^148m2Tb , colspan="3" style="text-indent:2em" , 8618.6(10) keV , 1.310(7) µs , , , (27+) , , , - , rowspan=2, ¹⁴⁹Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 84 , rowspan=2, 148.923246(5) , rowspan=2, 4.118(25) h , β⁺ (83.3%) , ¹⁴⁹Gd , rowspan=2, 1/2+ , rowspan=2, , rowspan=2, , - , α (16.7%) , ¹⁴⁵Eu , - , rowspan=2 style="text-indent:1em" , ^149mTb , rowspan=2 colspan="3" style="text-indent:2em" , 35.78(13) keV , rowspan=2, 4.16(4) min , β⁺ (99.97%) , ¹⁴⁹Gd , rowspan=2, 11/2− , rowspan=2, , rowspan=2, , - , α (.022%) , ¹⁴⁵Eu , - , rowspan=2, ¹⁵⁰Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 85 , rowspan=2, 149.923660(8) , rowspan=2, 3.48(16) h , β⁺ (99.95%) , ¹⁵⁰Gd , rowspan=2, (2−) , rowspan=2, , rowspan=2, , - , α (.05%) , ¹⁴⁶Eu , - , rowspan=2 style="text-indent:1em" , ^150mTb , rowspan=2 colspan="3" style="text-indent:2em" , 457(29) keV , rowspan=2, 5.8(2) min , β⁺ , ¹⁵⁰Gd , rowspan=2, 9+ , rowspan=2, , rowspan=2, , - , IT (rare) , ¹⁵⁰Tb , - , rowspan=2, ¹⁵¹Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 86 , rowspan=2, 150.923103(5) , rowspan=2, 17.609(1) h , β⁺ (99.99%) , ¹⁵¹Gd , rowspan=2, 1/2(+) , rowspan=2, , rowspan=2, , - , α (.0095%) , ¹⁴⁷Eu , - , rowspan=2 style="text-indent:1em" , ^151mTb , rowspan=2 colspan="3" style="text-indent:2em" , 99.54(6) keV , rowspan=2, 25(3) s , IT (93.8%) , ¹⁵¹Tb , rowspan=2, (11/2−) , rowspan=2, , rowspan=2, , - , β⁺ (6.2%) , ¹⁵¹Gd , - , rowspan=2, ¹⁵²Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 87 , rowspan=2, 151.92407(4) , rowspan=2, 17.5(1) h , β⁺ , ''¹⁵²Gd'' , rowspan=2, 2− , rowspan=2, , rowspan=2, , - , α (7×10⁻⁷%) , ¹⁴⁸Eu , - , style="text-indent:1em" , ^152m1Tb , colspan="3" style="text-indent:2em" , 342.15(16) keV , 0.96 µs , , , 5− , , , - , rowspan=2 style="text-indent:1em" , ^152m2Tb , rowspan=2 colspan="3" style="text-indent:2em" , 501.74(19) keV , rowspan=2, 4.2(1) min , IT (78.8%) , ¹⁵²Tb , rowspan=2, 8+ , rowspan=2, , rowspan=2, , - , β⁺ (21.2%) , ''¹⁵²Gd'' , - , ¹⁵³Tb , style="text-align:right" , 65 , style="text-align:right" , 88 , 152.923435(5) , 2.34(1) d , β⁺ , ¹⁵³Gd , 5/2+ , , , - , style="text-indent:1em" , ^153mTb , colspan="3" style="text-indent:2em" , 163.175(5) keV , 186(4) µs , , , 11/2− , , , - , rowspan=2, ¹⁵⁴Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 89 , rowspan=2, 153.92468(5) , rowspan=2, 21.5(4) h , β⁺ (99.9%) , ¹⁵⁴Gd , rowspan=2, 0(+#) , rowspan=2, , rowspan=2, , - , β⁻ (.1%) , ¹⁵⁴Dy , - , rowspan=3 style="text-indent:1em" , ^154m1Tb , rowspan=3 colspan="3" style="text-indent:2em" , 12(7) keV , rowspan=3, 9.4(4) h , β⁺ (78.2%) , ¹⁵⁴Gd , rowspan=3, 3− , rowspan=3, , rowspan=3, , - , IT (21.8%) , ¹⁵⁴Tb , - , β⁻ (.1%) , ¹⁵⁴Dy , - , style="text-indent:1em" , ^154m2Tb , colspan="3" style="text-indent:2em" , 200(150)# keV , 22.7(5) h , , , 7− , , , - , style="text-indent:1em" , ^154m3Tb , colspan="3" style="text-indent:2em" , 0+Z keV , 513(42) ns , , , , , , - , ¹⁵⁵Tb , style="text-align:right" , 65 , style="text-align:right" , 90 , 154.923505(13) , 5.32(6) d , EC , ¹⁵⁵Gd , 3/2+ , , , - , rowspan=2, ¹⁵⁶Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 91 , rowspan=2, 155.924747(5) , rowspan=2, 5.35(10) d , β⁺ , ¹⁵⁶Gd , rowspan=2, 3− , rowspan=2, , rowspan=2, , - , β⁻ (rare) , ¹⁵⁶Dy , - , style="text-indent:1em" , ^156m1Tb , colspan="3" style="text-indent:2em" , 54(3) keV , 24.4(10) h , IT , ¹⁵⁶Tb , (7−) , , , - , style="text-indent:1em" , ^156m2Tb , colspan="3" style="text-indent:2em" , 88.4(2) keV , 5.3(2) h , , , (0+) , , , - , ¹⁵⁷Tb , style="text-align:right" , 65 , style="text-align:right" , 92 , 156.9240246(27) , 71(7) y , EC , ¹⁵⁷Gd , 3/2+ , , , - , rowspan=2, ¹⁵⁸Tb , rowspan=2 style="text-align:right" , 65 , rowspan=2 style="text-align:right" , 93 , rowspan=2, 157.9254131(28) , rowspan=2, 180(11) y , β⁺ (83.4%) , ¹⁵⁸Gd , rowspan=2, 3− , rowspan=2, , rowspan=2, , - , β⁻ (16.6%) , ¹⁵⁸Dy , - , rowspan=3 style="text-indent:1em" , ^158m1Tb , rowspan=3 colspan="3" style="text-indent:2em" , 110.3(12) keV , rowspan=3, 10.70(17) s , IT (99.39%) , ¹⁵⁸Tb , rowspan=3, 0− , rowspan=3, , rowspan=3, , - , β⁻ (.6%) , ¹⁵⁸Dy , - , β⁺ (.01%) , ¹⁵⁸Gd , - , style="text-indent:1em" , ^158m2Tb , colspan="3" style="text-indent:2em" , 388.37(15) keV , 0.40(4) ms , , , 7− , , , - , ¹⁵⁹Tb Fission product , style="text-align:right" , 65 , style="text-align:right" , 94 , 158.9253468(27) , colspan=3 align=center, StableTheoretically capable of spontaneous fission , 3/2+ , 1.0000 , , - , ¹⁶⁰Tb , style="text-align:right" , 65 , style="text-align:right" , 95 , 159.9271676(27) , 72.3(2) d , β⁻ , ¹⁶⁰Dy , 3− , , , - , ¹⁶¹Tb , style="text-align:right" , 65 , style="text-align:right" , 96 , 160.9275699(28) , 6.906(19) d , β⁻ , ¹⁶¹Dy , 3/2+ , , , - , ¹⁶²Tb , style="text-align:right" , 65 , style="text-align:right" , 97 , 161.92949(4) , 7.60(15) min , β⁻ , ¹⁶²Dy , 1− , , , - , ¹⁶³Tb , style="text-align:right" , 65 , style="text-align:right" , 98 , 162.930648(5) , 19.5(3) min , β⁻ , ¹⁶³Dy , 3/2+ , , , - , ¹⁶⁴Tb , style="text-align:right" , 65 , style="text-align:right" , 99 , 163.93335(11) , 3.0(1) min , β⁻ , ¹⁶⁴Dy , (5+) , , , - , ¹⁶⁵Tb , style="text-align:right" , 65 , style="text-align:right" , 100 , 164.93488(21)# , 2.11(10) min , β⁻ , ^165mDy , 3/2+# , , , - , ¹⁶⁶Tb , style="text-align:right" , 65 , style="text-align:right" , 101 , 165.93799(11) , 25.6(22) s , β⁻ , ¹⁶⁶Dy , , , , - , ¹⁶⁷Tb , style="text-align:right" , 65 , style="text-align:right" , 102 , 166.94005(43)# , 19.4(27) s , β⁻ , ¹⁶⁷Dy , 3/2+# , , , - , ¹⁶⁸Tb , style="text-align:right" , 65 , style="text-align:right" , 103 , 167.94364(54)# , 8.2(13) s , β⁻ , ¹⁶⁸Dy , 4−# , , , - , ¹⁶⁹Tb , style="text-align:right" , 65 , style="text-align:right" , 104 , 168.94622(64)# , 5.13(32) s , β⁻ , ¹⁶⁹Dy , 3/2+# , , , - , ¹⁷⁰Tb , style="text-align:right" , 65 , style="text-align:right" , 105 , 169.95025(75)# , 960(78) ms , β⁻ , ¹⁷⁰Dy , , , , - , ¹⁷¹Tb , style="text-align:right" , 65 , style="text-align:right" , 106 , 170.95330(86)# , 1.23(10) s , β⁻ , ¹⁷¹Dy , 3/2+# , , , - , ¹⁷²Tb , style="text-align:right" , 65 , style="text-align:right" , 107 , , 760(190) ms , β⁻ , ¹⁷²Dy , 6+# , ,

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Terbium

Terbium Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with w ...