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Standard atomic weight Ar°(Cd) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Naturally occurring cadmium (48Cd) is composed of 8 isotopes. For two of them, natural radioactivity was observed, and three others are predicted to be radioactive but their decays have not been observed, due to extremely long half-lives. The two natural radioactive isotopes are 113Cd (beta decay, half-life is 8.04 × 1015 years) and 116Cd (two-neutrino double beta decay, half-life is 2.8 × 1019 years). The other three are 106Cd, 108Cd (double electron capture), and 114Cd (double beta decay); only lower limits on their half-life times have been set. Three isotopes—110Cd, 111Cd, and 112Cd—are theoretically stable. Among the isotopes absent in natural cadmium, the most long-lived are 109Cd with a half-life of 462.6 days, and 115Cd with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives that are less than 2.5 hours and the majority of these have half-lives that are less than 5 minutes. This element also has 12 known meta states, with the most stable being 113mCd (t1/2 14.1 years), 115mCd (t1/2 44.6 days) and 117mCd (t1/2 3.36 hours).
The known isotopes of cadmium range in atomic mass from 94.950 u (95Cd) to 131.946 u (132Cd). The primary decay mode before the second most abundant stable isotope, 112Cd, is electron capture and the primary modes after are beta emission and electron capture. The primary decay product before 112Cd is element 47 (silver) and the primary product after is element 49 (indium).
A 2021 study has shown at high ionic strengths, Cd isotope fractionation mainly depends on its complexation with carboxylic sites. At low ionic strengths, nonspecific Cd binding induced by electrostatic attractions plays a dominant role and promotes Cd isotope fractionation during complexation. [4]
Nuclide [n 1] | Z | N | Isotopic mass (Da) [n 2] [n 3] | Half-life [n 4] | Decay mode [n 5] | Daughter isotope [n 6] [n 7] | Spin and parity [n 8] [n 9] | Natural abundance (mole fraction) | |||||||||||
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Excitation energy [n 9] | Normal proportion | Range of variation | |||||||||||||||||
95Cd | 48 | 47 | 94.94987(64)# | 5# ms | 9/2+# | ||||||||||||||
96Cd | 48 | 48 | 95.93977(54)# | 1# s | β+ | 96Ag | 0+ | ||||||||||||
97Cd | 48 | 49 | 96.93494(43)# | 2.8(6) s | β+ (>99.9%) | 97Ag | 9/2+# | ||||||||||||
β+, p (<.1%) | 96Pd | ||||||||||||||||||
98Cd | 48 | 50 | 97.92740(8) | 9.2(3) s | β+ (99.975%) | 98Ag | 0+ | ||||||||||||
β+, p (.025%) | 97Ag | ||||||||||||||||||
98mCd | 2427.5(6) keV | 190(20) ns | 8+# | ||||||||||||||||
99Cd | 48 | 51 | 98.92501(22)# | 16(3) s | β+ (99.78%) | 99Ag | (5/2+) | ||||||||||||
β+, p (.21%) | 98Pd | ||||||||||||||||||
β+, α (10−4%) | 95Rh | ||||||||||||||||||
100Cd | 48 | 52 | 99.92029(10) | 49.1(5) s | β+ | 100Ag | 0+ | ||||||||||||
101Cd | 48 | 53 | 100.91868(16) | 1.36(5) min | β+ | 101Ag | (5/2+) | ||||||||||||
102Cd | 48 | 54 | 101.91446(3) | 5.5(5) min | β+ | 102Ag | 0+ | ||||||||||||
103Cd | 48 | 55 | 102.913419(17) | 7.3(1) min | β+ | 103Ag | 5/2+ | ||||||||||||
104Cd | 48 | 56 | 103.909849(10) | 57.7(10) min | β+ | 104Ag | 0+ | ||||||||||||
105Cd | 48 | 57 | 104.909468(12) | 55.5(4) min | β+ | 105Ag | 5/2+ | ||||||||||||
106Cd | 48 | 58 | 105.906459(6) | Observationally Stable [n 10] | 0+ | 0.0125(6) | |||||||||||||
107Cd | 48 | 59 | 106.906618(6) | 6.50(2) h | β+ | 107mAg | 5/2+ | ||||||||||||
108Cd | 48 | 60 | 107.904184(6) | Observationally Stable [n 11] | 0+ | 0.0089(3) | |||||||||||||
109Cd | 48 | 61 | 108.904982(4) | 461.4(12) d | EC | 109Ag | 5/2+ | ||||||||||||
109m1Cd | 59.6(4) keV | 12(2) μs | 1/2+ | ||||||||||||||||
109m2Cd | 463.0(5) keV | 10.9(5) μs | 11/2 | ||||||||||||||||
110Cd | 48 | 62 | 109.9030021(29) | Stable | 0+ | 0.1249(18) | |||||||||||||
111Cd [n 12] | 48 | 63 | 110.9041781(29) | Stable | 1/2+ | 0.1280(12) | |||||||||||||
111mCd | 396.214(21) keV | 48.50(9) min | IT | 111Cd | 11/2− | ||||||||||||||
112Cd [n 12] | 48 | 64 | 111.9027578(29) | Stable | 0+ | 0.2413(21) | |||||||||||||
113Cd [n 12] [n 13] | 48 | 65 | 112.9044017(29) | 8.04(5)×1015 y | β− | 113In | 1/2+ | 0.1222(12) | |||||||||||
113mCd [n 12] | 263.54(3) keV | 14.1(5) y | β− (99.86%) | 113In | 11/2− | ||||||||||||||
IT (.139%) | 113Cd | ||||||||||||||||||
114Cd [n 12] | 48 | 66 | 113.9033585(29) | Observationally Stable [n 14] | 0+ | 0.2873(42) | |||||||||||||
115Cd [n 12] | 48 | 67 | 114.9054310(29) | 53.46(5) h | β− | 115mIn | 1/2+ | ||||||||||||
115mCd | 181.0(5) keV | 44.56(24) d | β− | 115mIn | (11/2)− | ||||||||||||||
116Cd [n 12] [n 13] | 48 | 68 | 115.904756(3) | 2.8(2)×1019 y | β−β− | 116Sn | 0+ | 0.0749(18) | |||||||||||
117Cd | 48 | 69 | 116.907219(4) | 2.49(4) h | β− | 117mIn | 1/2+ | ||||||||||||
117mCd | 136.4(2) keV | 3.36(5) h | β− | 117mIn | (11/2)− | ||||||||||||||
118Cd | 48 | 70 | 117.906915(22) | 50.3(2) min | β− | 118In | 0+ | ||||||||||||
119Cd | 48 | 71 | 118.90992(9) | 2.69(2) min | β− | 119mIn | (3/2+) | ||||||||||||
119mCd | 146.54(11) keV | 2.20(2) min | β− | 119mIn | (11/2−)# | ||||||||||||||
120Cd | 48 | 72 | 119.90985(2) | 50.80(21) s | β− | 120In | 0+ | ||||||||||||
121Cd | 48 | 73 | 120.91298(9) | 13.5(3) s | β− | 121mIn | (3/2+) | ||||||||||||
121mCd | 214.86(15) keV | 8.3(8) s | β− | 121mIn | (11/2−) | ||||||||||||||
122Cd | 48 | 74 | 121.91333(5) | 5.24(3) s | β− | 122In | 0+ | ||||||||||||
123Cd | 48 | 75 | 122.91700(4) | 2.10(2) s | β− | 123mIn | (3/2)+ | ||||||||||||
123mCd | 316.52(23) keV | 1.82(3) s | β− | 123In | (11/2−) | ||||||||||||||
IT | 123Cd | ||||||||||||||||||
124Cd | 48 | 76 | 123.91765(7) | 1.25(2) s | β− | 124In | 0+ | ||||||||||||
125Cd | 48 | 77 | 124.92125(7) | 0.65(2) s | β− | 125mIn | (3/2+)# | ||||||||||||
125mCd | 50(70) keV | 570(90) ms | β− | 125In | 11/2−# | ||||||||||||||
126Cd | 48 | 78 | 125.92235(6) | 0.515(17) s | β− | 126In | 0+ | ||||||||||||
127Cd | 48 | 79 | 126.92644(8) | 0.37(7) s | β− | 127mIn | (3/2+) | ||||||||||||
128Cd | 48 | 80 | 127.92776(32) | 0.28(4) s | β− | 128In | 0+ | ||||||||||||
129Cd | 48 | 81 | 128.93215(32)# | 242(8) ms | β− (>99.9%) | 129In | 3/2+# | ||||||||||||
IT (<.1%) | 129Cd | ||||||||||||||||||
129mCd | 0(200)# keV | 104(6) ms | 11/2−# | ||||||||||||||||
130Cd | 48 | 82 | 129.9339(3) | 162(7) ms | β− (96%) | 130In | 0+ | ||||||||||||
β−, n (4%) | 129In | ||||||||||||||||||
131Cd | 48 | 83 | 130.94067(32)# | 68(3) ms | 7/2−# | ||||||||||||||
132Cd | 48 | 84 | 131.94555(54)# | 97(10) ms | 0+ | ||||||||||||||
This table header & footer: |
EC: | Electron capture |
IT: | Isomeric transition |
n: | Neutron emission |
p: | Proton emission |
t½ (year) | Yield (%) | Q (keV) | βγ | |
---|---|---|---|---|
155Eu | 4.76 | 0.0803 | 252 | βγ |
85Kr | 10.76 | 0.2180 | 687 | βγ |
113mCd | 14.1 | 0.0008 | 316 | β |
90Sr | 28.9 | 4.505 | 2826 | β |
137Cs | 30.23 | 6.337 | 1176 | βγ |
121mSn | 43.9 | 0.00005 | 390 | βγ |
151Sm | 88.8 | 0.5314 | 77 | β |
Cadmium-113m is a cadmium radioisotope and nuclear isomer with a half-life of 14.1 years. In a normal thermal reactor, it has a very low fission product yield, plus its large neutron capture cross section means that most of even the small amount produced is destroyed in the course of the nuclear fuel's burnup; thus, this isotope is not a significant contributor to nuclear waste.
Fast fission or fission of some heavier actinides [ which? ] will produce 113mCd at higher yields.
Protactinium (91Pa) has no stable isotopes. The four naturally occurring isotopes allow a standard atomic weight to be given.
Naturally occurring tungsten (74W) consists of five isotopes. Four are considered stable (182W, 183W, 184W, and 186W) and one is slightly radioactive, 180W, with an extremely long half-life of 1.8 ± 0.2 exayears (1018 years). On average, two alpha decays of 180W occur per gram of natural tungsten per year, so for most practical purposes, 180W can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed to do so. The other naturally occurring isotopes have not been observed to decay (they are observationally stable), and lower bounds for their half-lives have been established:
Naturally occurring ytterbium (70Yb) is composed of seven stable isotopes: 168Yb, 170Yb–174Yb, and 176Yb, with 174Yb being the most abundant. 30 radioisotopes have been characterized, with the most stable being 169Yb with a half-life of 32.014 days, 175Yb with a half-life of 4.185 days, and 166Yb with a half-life of 56.7 hours. All of the remaining radioactive isotopes have half-lives that are less than 2 hours, and the majority of these have half-lives that are less than 20 minutes. This element also has 18 meta states, with the most stable being 169mYb.
Naturally occurring terbium (65Tb) is composed of one stable isotope, 159Tb. Thirty-seven radioisotopes have been characterized, with the most stable being 158Tb with a half-life 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 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 states, with the most stable being 156m1Tb, 154m2Tb and 154m1Tb.
Naturally occurring gadolinium (64Gd) is composed of 6 stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd, and 1 radioisotope, 152Gd, with 158Gd being the most abundant (24.84% natural abundance). The predicted double beta decay of 160Gd has never been observed; only a lower limit on its half-life of more than 1.3×1021 years has been set experimentally.
Naturally occurring europium (63Eu) is composed of two isotopes, 151Eu and 153Eu, with 153Eu being the most abundant (52.2% natural abundance). While 153Eu is observationally stable (theoretically can undergo alpha decay with half-life over 5.5×1017 years), 151Eu was found in 2007 to be unstable and undergo alpha decay. The half-life is measured to be (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 years which corresponds to 1 alpha decay per two minutes in every kilogram of natural europium. Besides the natural radioisotope 151Eu, 36 artificial radioisotopes have been characterized, with the most stable being 150Eu with a half-life of 36.9 years, 152Eu with a half-life of 13.516 years, 154Eu with a half-life of 8.593 years, and 155Eu with a half-life of 4.7612 years. The majority of the remaining radioactive isotopes, which range from 130Eu to 170Eu, have half-lives that are less than 12.2 seconds. This element also has 18 metastable isomers, with the most stable being 150mEu (t1/2 12.8 hours), 152m1Eu (t1/2 9.3116 hours) and 152m5Eu (t1/2 96 minutes).
Promethium (61Pm) is an artificial element, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was first synthesized in 1945.
Naturally occurring neodymium (60Nd) is composed of 5 stable isotopes, 142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant (27.2% natural abundance), and 2 long-lived radioisotopes, 144Nd and 150Nd. In all, 33 radioisotopes of neodymium have been characterized up to now, with the most stable being naturally occurring isotopes 144Nd (alpha decay, a half-life (t1/2) of 2.29×1015 years) and 150Nd (double beta decay, t1/2 of 7×1018 years), and for practical purposes they can be considered to be stable as well. All of the remaining radioactive isotopes have half-lives that are less than 12 days, and the majority of these have half-lives that are less than 70 seconds; the most stable artificial isotope is 147Nd with a half-life of 10.98 days. This element also has 13 known meta states with the most stable being 139mNd (t1/2 5.5 hours), 135mNd (t1/2 5.5 minutes) and 133m1Nd (t1/2 ~70 seconds).
Naturally occurring praseodymium (59Pr) is composed of one stable isotope, 141Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143Pr, with a half-life of 13.57 days and 142Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than 5.985 hours and the majority of these have half-lives that are less than 33 seconds. This element also has 15 meta states with the most stable being 138mPr, 142mPr and 134mPr.
Naturally occurring cerium (58Ce) is composed of 4 stable isotopes: 136Ce, 138Ce, 140Ce, and 142Ce, with 140Ce being the most abundant and the only one theoretically stable; 136Ce, 138Ce, and 142Ce are predicted to undergo double beta decay but this process has never been observed. There are 35 radioisotopes that have been characterized, with the most stable being 144Ce, with a half-life of 284.893 days; 139Ce, with a half-life of 137.640 days and 141Ce, with a half-life of 32.501 days. All of the remaining radioactive isotopes have half-lives that are less than 4 days and the majority of these have half-lives that are less than 10 minutes. This element also has 10 meta states.
Naturally occurring lanthanum (57La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). There are 39 radioisotopes that have been characterized, with the most stable being 138La, with a half-life of 1.02×1011 years; 137La, with a half-life of 60,000 years and 140La, with a half-life of 1.6781 days. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these have half-lives that are less than 1 minute. This element also has 12 nuclear isomers, the longest-lived of which is 132mLa, with a half-life of 24.3 minutes. Lighter isotopes mostly decay to isotopes of barium and heavy ones mostly decay to isotopes of cerium. 138La can decay to both.
Naturally occurring barium (56Ba) is a mix of six stable isotopes and one very long-lived radioactive primordial isotope, barium-130, identified as being unstable by geochemical means (from analysis of the presence of its daughter xenon-130 in rocks) in 2001. This nuclide decays by double electron capture (absorbing two electrons and emitting two neutrinos), with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe).
There are 39 known isotopes and 17 nuclear isomers of tellurium (52Te), with atomic masses that range from 104 to 142. These are listed in the table below.
Tin (50Sn) is the element with the greatest number of stable isotopes. This is probably related to the fact that 50 is a "magic number" of protons. In addition, twenty-nine unstable tin isotopes are known, including tin-100 (100Sn) and tin-132 (132Sn), which are both "doubly magic". The longest-lived tin radioisotope is tin-126 (126Sn), with a half-life of 230,000 years. The other 28 radioisotopes have half-lives of less than a year.
Natural palladium (46Pd) is composed of six stable isotopes, 102Pd, 104Pd, 105Pd, 106Pd, 108Pd, and 110Pd, although 102Pd and 110Pd are theoretically unstable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years, 103Pd with a half-life of 17 days, and 100Pd with a half-life of 3.63 days. Twenty-three other radioisotopes have been characterized with atomic weights ranging from 90.949 u (91Pd) to 128.96 u (129Pd). Most of these have half-lives that are less than 30 minutes except 101Pd, 109Pd, and 112Pd.
Naturally occurring ruthenium (44Ru) is composed of seven stable isotopes. Additionally, 27 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are 106Ru, with a half-life of 373.59 days; 103Ru, with a half-life of 39.26 days and 97Ru, with a half-life of 2.9 days.
Naturally occurring zirconium (40Zr) is composed of four stable isotopes (of which one may in the future be found radioactive), and one very long-lived radioisotope (96Zr), a primordial nuclide that decays via double beta decay with an observed half-life of 2.0×1019 years; it can also undergo single beta decay, which is not yet observed, but the theoretically predicted value of t1/2 is 2.4×1020 years. The second most stable radioisotope is 93Zr, which has a half-life of 1.53 million years. Thirty other radioisotopes have been observed. All have half-lives less than a day except for 95Zr (64.02 days), 88Zr (83.4 days), and 89Zr (78.41 hours). The primary decay mode is electron capture for isotopes lighter than 92Zr, and the primary mode for heavier isotopes is beta decay.
The alkaline earth metal strontium (38Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Its standard atomic weight is 87.62(1).
Arsenic (33As) has 32 known isotopes and at least 10 isomers. Only one of these isotopes, 75As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73As with a half-life of 80 days.
Naturally occurring scandium (21Sc) is composed of one stable isotope, 45Sc. Twenty-seven radioisotopes have been characterized, with the most stable being 46Sc with a half-life of 83.8 days, 47Sc with a half-life of 3.35 days, and 48Sc with a half-life of 43.7 hours and 44Sc with a half-life of 3.97 hours. All the remaining isotopes have half-lives that are less than four hours, and the majority of these have half-lives that are less than two minutes, the least stable being proton unbound 39Sc with a half-life shorter than 300 nanoseconds. This element also has 13 meta states with the most stable being 44m2Sc.