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Standard atomic weight Ar°(Ir) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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There are two natural isotopes of iridium (77Ir), and 37 radioisotopes, the most stable radioisotope being 192Ir with a half-life of 73.83 days, and many nuclear isomers, the most stable of which is 192m2Ir with a half-life of 241 years. All other isomers have half-lives under a year, most under a day. All isotopes of iridium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed. [4]
Nuclide [5] [n 1] | Z | N | Isotopic mass (Da) [6] [n 2] [n 3] | Half-life [n 4] | Decay mode [n 5] | Daughter isotope [n 6] [n 7] | Spin and parity [n 8] [n 4] | Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy [n 4] | Normal proportion | Range of variation | |||||||||||||||||
164Ir [7] | 77 | 87 | 163.99220(44)# | <0.5 µs | p? | 163Os | 2−# | ||||||||||||
164mIr | 270(110)# keV | 70(10) µs | p (96%) | 163Os | 9+# | ||||||||||||||
α (4%) | 160mRe | ||||||||||||||||||
165Ir | 77 | 88 | 164.98752(23)# | 1.20+0.82 −0.74 μs [8] | p | 164Os | (1/2+) | ||||||||||||
165mIr [9] | ~255 keV | 340(40) µs | p (88%) | 164Os | (11/2−) | ||||||||||||||
α (12%) | 161mRe | ||||||||||||||||||
166Ir | 77 | 89 | 165.98582(22)# | 10.5(22) ms | α (93%) | 162Re | (2−) | ||||||||||||
p (7%) | 165Os | ||||||||||||||||||
166mIr | 172(6) keV | 15.1(9) ms | α (98.2%) | 162Re | (9+) | ||||||||||||||
p (1.8%) | 165Os | ||||||||||||||||||
167Ir | 77 | 90 | 166.981665(20) | 35.2(20) ms | α (48%) | 163Re | 1/2+ | ||||||||||||
p (32%) | 166Os | ||||||||||||||||||
β+ (20%) | 167Os | ||||||||||||||||||
167mIr | 175.3(22) keV | 30.0(6) ms | α (80%) | 163Re | 11/2− | ||||||||||||||
β+ (20%) | 167Os | ||||||||||||||||||
p (.4%) | 166Os | ||||||||||||||||||
168Ir | 77 | 91 | 167.97988(16)# | 161(21) ms | α | 164Re | (2-) | ||||||||||||
β+ (rare) | 168Os | ||||||||||||||||||
168mIr | 50(100)# keV | 125(40) ms | α | 164Re | (9+) | ||||||||||||||
169Ir | 77 | 92 | 168.976295(28) | 780(360) ms [0.64(+46−24) s] | α | 165Re | (1/2+) | ||||||||||||
β+ (rare) | 169Os | ||||||||||||||||||
169mIr | 154(24) keV | 308(22) ms | α (72%) | 165Re | (11/2−) | ||||||||||||||
β+ (28%) | 169Os | ||||||||||||||||||
170Ir | 77 | 93 | 169.97497(11)# | 910(150) ms [0.87(+18−12) s] | β+ (64%) | 170Os | low# | ||||||||||||
α (36%) | 166Re | ||||||||||||||||||
170mIr | 160(50)# keV | 440(60) ms | α (36%) | 166Re | (8+) | ||||||||||||||
β+ | 170Os | ||||||||||||||||||
IT | 170Ir | ||||||||||||||||||
171Ir | 77 | 94 | 170.97163(4) | 3.6(10) s [3.2(+13−7) s] | α (58%) | 167Re | 1/2+ | ||||||||||||
β+ (42%) | 171Os | ||||||||||||||||||
171mIr | 180(30)# keV | 1.40(10) s | (11/2−) | ||||||||||||||||
172Ir | 77 | 95 | 171.970610(30) | 4.4(3) s | β+ (98%) | 172Os | (3+) | ||||||||||||
α (2%) | 168Re | ||||||||||||||||||
172mIr | 280(100)# keV | 2.0(1) s | β+ (77%) | 172Os | (7+) | ||||||||||||||
α (23%) | 168Re | ||||||||||||||||||
173Ir | 77 | 96 | 172.967502(15) | 9.0(8) s | β+ (93%) | 173Os | (3/2+,5/2+) | ||||||||||||
α (7%) | 169Re | ||||||||||||||||||
173mIr | 253(27) keV | 2.20(5) s | β+ (88%) | 173Os | (11/2−) | ||||||||||||||
α (12%) | 169Re | ||||||||||||||||||
174Ir | 77 | 97 | 173.966861(30) | 7.9(6) s | β+ (99.5%) | 174Os | (3+) | ||||||||||||
α (.5%) | 170Re | ||||||||||||||||||
174mIr | 193(11) keV | 4.9(3) s | β+ (99.53%) | 174Os | (7+) | ||||||||||||||
α (.47%) | 170Re | ||||||||||||||||||
175Ir | 77 | 98 | 174.964113(21) | 9(2) s | β+ (99.15%) | 175Os | (5/2−) | ||||||||||||
α (.85%) | 171Re | ||||||||||||||||||
176Ir | 77 | 99 | 175.963649(22) | 8.3(6) s | β+ (97.9%) | 176Os | |||||||||||||
α (2.1%) | 172Re | ||||||||||||||||||
177Ir | 77 | 100 | 176.961302(21) | 30(2) s | β+ (99.94%) | 177Os | 5/2− | ||||||||||||
α (.06%) | 173Re | ||||||||||||||||||
178Ir | 77 | 101 | 177.961082(21) | 12(2) s | β+ | 178Os | |||||||||||||
179Ir | 77 | 102 | 178.959122(12) | 79(1) s | β+ | 179Os | (5/2)− | ||||||||||||
180Ir | 77 | 103 | 179.959229(23) | 1.5(1) min | β+ | 180Os | (4,5)(+#) | ||||||||||||
181Ir | 77 | 104 | 180.957625(28) | 4.90(15) min | β+ | 181Os | (5/2)− | ||||||||||||
182Ir | 77 | 105 | 181.958076(23) | 15(1) min | β+ | 182Os | (3+) | ||||||||||||
183Ir | 77 | 106 | 182.956846(27) | 57(4) min | β+ ( 99.95%) | 183Os | 5/2− | ||||||||||||
α (.05%) | 179Re | ||||||||||||||||||
184Ir | 77 | 107 | 183.95748(3) | 3.09(3) h | β+ | 184Os | 5− | ||||||||||||
184m1Ir | 225.65(11) keV | 470(30) µs | 3+ | ||||||||||||||||
184m2Ir | 328.40(24) keV | 350(90) ns | (7)+ | ||||||||||||||||
185Ir | 77 | 108 | 184.95670(3) | 14.4(1) h | β+ | 185Os | 5/2− | ||||||||||||
186Ir | 77 | 109 | 185.957946(18) | 16.64(3) h | β+ | 186Os | 5+ | ||||||||||||
186mIr | 0.8(4) keV | 1.92(5) h | β+ | 186Os | 2− | ||||||||||||||
IT (rare) | 186Ir | ||||||||||||||||||
187Ir | 77 | 110 | 186.957363(7) | 10.5(3) h | β+ | 187Os | 3/2+ | ||||||||||||
187m1Ir | 186.15(4) keV | 30.3(6) ms | IT | 187Ir | 9/2− | ||||||||||||||
187m2Ir | 433.81(9) keV | 152(12) ns | 11/2− | ||||||||||||||||
188Ir | 77 | 111 | 187.958853(8) | 41.5(5) h | β+ | 188Os | 1− | ||||||||||||
188mIr | 970(30) keV | 4.2(2) ms | IT | 188Ir | 7+# | ||||||||||||||
β+ (rare) | 188Os | ||||||||||||||||||
189Ir | 77 | 112 | 188.958719(14) | 13.2(1) d | EC | 189Os | 3/2+ | ||||||||||||
189m1Ir | 372.18(4) keV | 13.3(3) ms | IT | 189Ir | 11/2− | ||||||||||||||
189m2Ir | 2333.3(4) keV | 3.7(2) ms | (25/2)+ | ||||||||||||||||
190Ir | 77 | 113 | 189.9605460(18) | 11.78(10) d | β+ | 190Os | 4− | ||||||||||||
190m1Ir | 26.1(1) keV | 1.120(3) h | IT | 190Ir | (1−) | ||||||||||||||
190m2Ir | 36.154(25) keV | >2 µs | (4)+ | ||||||||||||||||
190m3Ir | 376.4(1) keV | 3.087(12) h | (11)− | ||||||||||||||||
191Ir | 77 | 114 | 190.9605940(18) | Observationally Stable [n 9] | 3/2+ | 0.373(2) | |||||||||||||
191m1Ir | 171.24(5) keV | 4.94(3) s | IT | 191Ir | 11/2− | ||||||||||||||
191m2Ir | 2120(40) keV | 5.5(7) s | |||||||||||||||||
192Ir | 77 | 115 | 191.9626050(18) | 73.827(13) d | β− (95.24%) | 192Pt | 4+ | ||||||||||||
EC (4.76%) | 192Os | ||||||||||||||||||
192m1Ir | 56.720(5) keV | 1.45(5) min | 1− | ||||||||||||||||
192m2Ir | 168.14(12) keV | 241(9) y | (11−) | ||||||||||||||||
193Ir | 77 | 116 | 192.9629264(18) | Observationally Stable [n 10] | 3/2+ | 0.627(2) | |||||||||||||
193mIr | 80.240(6) keV | 10.53(4) d | IT | 193Ir | 11/2− | ||||||||||||||
194Ir | 77 | 117 | 193.9650784(18) | 19.28(13) h | β− | 194Pt | 1− | ||||||||||||
194m1Ir | 147.078(5) keV | 31.85(24) ms | IT | 194Ir | (4+) | ||||||||||||||
194m2Ir | 370(70) keV | 171(11) d | (10,11)(−#) | ||||||||||||||||
195Ir | 77 | 118 | 194.9659796(18) | 2.5(2) h | β− | 195Pt | 3/2+ | ||||||||||||
195mIr | 100(5) keV | 3.8(2) h | β− (95%) | 195Pt | 11/2− | ||||||||||||||
IT (5%) | 195Ir | ||||||||||||||||||
196Ir | 77 | 119 | 195.96840(4) | 52(1) s | β− | 196Pt | (0−) | ||||||||||||
196mIr | 210(40) keV | 1.40(2) h | β− (99.7%) | 196Pt | (10,11−) | ||||||||||||||
IT | 196Ir | ||||||||||||||||||
197Ir | 77 | 120 | 196.969653(22) | 5.8(5) min | β− | 197Pt | 3/2+ | ||||||||||||
197mIr | 115(5) keV | 8.9(3) min | β− (99.75%) | 197Pt | 11/2− | ||||||||||||||
IT (.25%) | 197Ir | ||||||||||||||||||
198Ir | 77 | 121 | 197.97228(21)# | 8(1) s | β− | 198Pt | |||||||||||||
199Ir | 77 | 122 | 198.97380(4) | 7(5) s | β− | 199Pt | 3/2+# | ||||||||||||
199mIr | 130(40)# keV | 235(90) ns | IT | 199Ir | 11/2−# | ||||||||||||||
200Ir | 77 | 123 | 199.976800(210)# | 43(6) s | β− | 200Pt | (2-, 3-) | ||||||||||||
201Ir | 77 | 124 | 200.978640(210)# | 21(5) s | β− | 201Pt | (3/2+) | ||||||||||||
202Ir | 77 | 125 | 201.981990(320)# | 11(3) s | β− | 202Pt | (2-) | ||||||||||||
202mIr | 2000(1000)# keV | 3.4(0.6) µs | IT | 202Ir | |||||||||||||||
This table header & footer: |
EC: | Electron capture |
IT: | Isomeric transition |
p: | Proton emission |
Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.83 days. [10] It decays by emitting beta (β) particles and gamma (γ) radiation. About 96% of 192Ir decays occur via emission of β and γ radiation, leading to 192Pt. Some of the β particles are captured by other 192Ir nuclei, which are then converted to 192Os. Electron capture is responsible for the remaining 4% of 192Ir decays. [11] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal. [12]
Iridium-192 is a very strong gamma ray emitter, with a gamma dose-constant of approximately 1.54 μSv·h−1·MBq −1 at 30 cm, and a specific activity of 341 TBq·g−1 (9.22 kCi·g−1). [13] [14] There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV.
The 192m2Ir isomer is unusual, both for its long half-life for an isomer, and that said half-life greatly exceeds that of the ground state of the same isotope.
Lead (82Pb) has four observationally stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series, the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series, terminates with the thallium isotope 205Tl. The three series terminating in lead represent the decay chain products of long-lived primordial 238U, 235U, and 232Th, respectively. However, each of them also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products. The fixed ratio of lead-204 to the primordial amounts of the other lead isotopes may be used as the baseline to estimate the extra amounts of radiogenic lead present in rocks as a result of decay from uranium and thorium..
Bismuth (83Bi) has 41 known isotopes, ranging from 184Bi to 224Bi. Bismuth has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as 208.98040(1). Although bismuth-209 is now known to be radioactive, it has classically been considered to be a stable isotope because it has a half-life of approximately 2.01×1019 years, which is more than a billion times the age of the universe. Besides 209Bi, the most stable bismuth radioisotopes are 210mBi with a half-life of 3.04 million years, 208Bi with a half-life of 368,000 years and 207Bi, with a half-life of 32.9 years, none of which occurs in nature. All other isotopes have half-lives under 1 year, most under a day. Of naturally occurring radioisotopes, the most stable is radiogenic 210Bi with a half-life of 5.012 days. 210mBi is unusual for being a nuclear isomer with a half-life multiple orders of magnitude longer than that of the ground state.
Thallium (81Tl) has 41 isotopes with atomic masses that range from 176 to 216. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years. 207Tl, with a half-life of 4.77 minutes, has the longest half-life of naturally occurring Tl radioisotopes. All isotopes of thallium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
There are seven stable isotopes of mercury (80Hg) with 202Hg being the most abundant (29.86%). The longest-lived radioisotopes are 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Most of the remaining 40 radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spin quantum numbers of 1/2 and 3/2 respectively. All isotopes of mercury are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed. These isotopes are predicted to undergo either alpha decay or double beta decay.
Naturally occurring platinum (78Pt) consists of five stable isotopes (192Pt, 194Pt, 195Pt, 196Pt, 198Pt) and one very long-lived (half-life 6.50×1011 years) radioisotope (190Pt). There are also 34 known synthetic radioisotopes, the longest-lived of which is 193Pt with a half-life of 50 years. All other isotopes have half-lives under a year, most under a day. All isotopes of platinum are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed. Platinum-195 is the most abundant isotope.
Natural hafnium (72Hf) consists of five observationally stable isotopes (176Hf, 177Hf, 178Hf, 179Hf, and 180Hf) and one very long-lived radioisotope, 174Hf, with a half-life of 7.0×1016 years. In addition, there are 34 known synthetic radioisotopes, the most stable of which is 182Hf with a half-life of 8.9×106 years. This extinct radionuclide is used in hafnium–tungsten dating to study the chronology of planetary differentiation.
Naturally occurring erbium (68Er) is composed of 6 stable isotopes, with 166Er being the most abundant. 39 radioisotopes have been characterized with between 74 and 112 neutrons, or 142 to 180 nucleons, with the most stable being 169Er with a half-life of 9.4 days, 172Er with a half-life of 49.3 hours, 160Er with a half-life of 28.58 hours, 165Er with a half-life of 10.36 hours, and 171Er with a half-life of 7.516 hours. All of the remaining radioactive isotopes have half-lives that are less than 3.5 hours, and the majority of these have half-lives that are less than 4 minutes. This element also has numerous meta states, with the most stable being 167mEr.
Natural holmium (67Ho) contains one observationally stable isotope, 165Ho. The below table lists 36 isotopes spanning 140Ho through 175Ho as well as 33 nuclear isomers. Among the known synthetic radioactive isotopes; the most stable one is 163Ho, with a half-life of 4,570 years. All other radioisotopes have half-lives not greater than 1.117 days in their ground states, and most have half-lives under 3 hours.
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).
Indium (49In) consists of two primordial nuclides, with the most common (~ 95.7%) nuclide (115In) being measurably though weakly radioactive. Its spin-forbidden decay has a half-life of 4.41×1014 years, much longer than the currently accepted age of the Universe.
Naturally occurring silver (47Ag) is composed of the two stable isotopes 107Ag and 109Ag in almost equal proportions, with 107Ag being slightly more abundant. Notably, silver is the only element with all stable istopes having nuclear spins of 1/2. Thus both 107Ag and 109Ag nuclei produce narrow lines in nuclear magnetic resonance spectra.
Selenium (34Se) has six natural isotopes that occur in significant quantities, along with the trace isotope 79Se, which occurs in minute quantities in uranium ores. Five of these isotopes are stable: 74Se, 76Se, 77Se, 78Se, and 80Se. The last three also occur as fission products, along with 79Se, which has a half-life of 327,000 years, and 82Se, which has a very long half-life (~1020 years, decaying via double beta decay to 82Kr) and for practical purposes can be considered to be stable. There are 23 other unstable isotopes that have been characterized, the longest-lived being 79Se with a half-life 327,000 years, 75Se with a half-life of 120 days, and 72Se with a half-life of 8.40 days. Of the other isotopes, 73Se has the longest half-life, 7.15 hours; most others have half-lives not exceeding 38 seconds.
Naturally occurring scandium (21Sc) is composed of one stable isotope, 45Sc. Twenty-five 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.
Potassium has 26 known isotopes from 31
K to 57
K, with the exception of still-unknown 32
K, as well as an unconfirmed report of 59
K. Three of those isotopes occur naturally: the two stable forms 39
K (93.3%) and 41
K (6.7%), and a very long-lived radioisotope 40
K (0.012%)
Argon (18Ar) has 26 known isotopes, from 29Ar to 54Ar and 1 isomer (32mAr), of which three are stable. On the Earth, 40Ar makes up 99.6% of natural argon. The longest-lived radioactive isotopes are 39Ar with a half-life of 268 years, 42Ar with a half-life of 32.9 years, and 37Ar with a half-life of 35.04 days. All other isotopes have half-lives of less than two hours, and most less than one minute. The least stable is 29Ar with a half-life of approximately 4×10−20 seconds.
Although phosphorus (15P) has 22 isotopes from 26P to 47P, only 31P is stable; as such, phosphorus is considered a monoisotopic element. The longest-lived radioactive isotopes are 33P with a half-life of 25.34 days and 32P with a half-life of 14.268 days. All others have half-lives of under 2.5 minutes, most under a second. The least stable known isotope is 47P, with a half-life of 2 milliseconds.
Silicon (14Si) has 23 known isotopes, with mass numbers ranging from 22 to 44. 28Si, 29Si (4.67%), and 30Si (3.1%) are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years, and it decays by beta emission to 32P and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds.
Sulfur (16S) has 23 known isotopes with mass numbers ranging from 27 to 49, four of which are stable: 32S (95.02%), 33S (0.75%), 34S (4.21%), and 36S (0.02%). The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium-4 nuclei, in the so-called alpha process of exploding type II supernovas.
Aluminium or aluminum (13Al) has 22 known isotopes from 22Al to 43Al and 4 known isomers. Only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2×105 y) occur naturally, however 27Al comprises nearly all natural aluminium. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. The standard atomic weight is 26.9815385(7). 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10Be has been used to study the role of sediment transport, deposition, and storage, as well as burial times, and erosion, on 105 to 106 year time scales. 26Al has also played a significant role in the study of meteorites.
Mendelevium (101Md) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 256Md in 1955. There are 17 known radioisotopes, ranging in atomic mass from 244Md to 260Md, and 5 isomers. The longest-lived isotope is 258Md with a half-life of 51.3 days, and the longest-lived isomer is 258mMd with a half-life of 57 minutes.