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Lawrencium (103Lr) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 258Lr in 1961. There are fourteen known isotopes from 251Lr to 266Lr, and seven isomers. The longest-lived known isotope is 266Lr with a half-life of 11 hours.
Nuclide [n 1] | Z | N | Isotopic mass (Da) [n 2] [n 3] | Half-life | Decay mode [n 4] | Daughter isotope | Spin and parity [n 5] [n 6] | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy [n 6] | |||||||||||||||||||
251Lr [3] | 103 | 148 | 251.09418(32)# | 24.4+7.0 −4.5 ms | α | 247Md | 7/2− | ||||||||||||
SF [4] [n 7] | (various) | ||||||||||||||||||
251mLr [3] | 117(27) keV | 42+42 −14 ms | α | 247Md | 1/2− | ||||||||||||||
252Lr [n 8] [5] | 103 | 149 | 252.09526(26)# | 369(75) ms [0.36+0.11 −0.07 s] | α (~98%) | 248Md | |||||||||||||
SF (~2%) | (various) | ||||||||||||||||||
β+? | 252No | ||||||||||||||||||
253Lr [6] | 103 | 150 | 253.09509(22)# | 632(46) ms [7] | α (>97%) | 249Md | (7/2−) | ||||||||||||
SF (1.0%) | (various) | ||||||||||||||||||
β+ (<2%) | 253No | ||||||||||||||||||
253mLr | 30(100)# keV | 1.32(14) s | α (>86%) | 249Md | (1/2−) | ||||||||||||||
SF (12%) | (various) | ||||||||||||||||||
β+ (<2%) | 253No | ||||||||||||||||||
254Lr [8] [9] | 103 | 151 | 254.096240(100) [10] | 11.9(9) s | α (71.7%) | 250Md | (4+) | ||||||||||||
β+ (28.3%) | 254No | ||||||||||||||||||
SF (<0.1%) | (various) | ||||||||||||||||||
254mLr | 110(6) keV [11] | 20.3(4.2) s | α | 250Md | (1-) | ||||||||||||||
β+ | 254No | ||||||||||||||||||
IT? | 254Lr | ||||||||||||||||||
255Lr [8] | 103 | 152 | 255.096562(19) | 31.1(1.1) s | α (85%) | 251Md | 1/2− [3] | ||||||||||||
β+ (15%) [12] | 255No | ||||||||||||||||||
SF (rare) | (various) | ||||||||||||||||||
255m1Lr [8] | 32(2) keV [11] | 2.54(5) s | IT (~60%) | 255Lr | (7/2−) | ||||||||||||||
α (~40%) | 251Md | ||||||||||||||||||
255m2Lr [8] | 796(12) keV | <1 μs | IT | 255m1Lr | (15/2+) | ||||||||||||||
255m3Lr [8] | 1465(12) keV | 1.78(0.05) ms | IT | 255m2Lr | (25/2+) | ||||||||||||||
256Lr [13] | 103 | 153 | 256.09849(9) | 27.9(1.0) s | α (85%) | 252Md | (0-,3-)# | ||||||||||||
β+ (15%) | 256No | ||||||||||||||||||
SF (<0.03%) | (various) | ||||||||||||||||||
257Lr [14] | 103 | 154 | 257.09942(5)# | 1.24+0.85 −0.36 s | α | 253Md | (9/2+,7/2-) | ||||||||||||
β+ (rare) | 257No | ||||||||||||||||||
SF (rare) | (various) | ||||||||||||||||||
257mLr [8] | 100(50)# keV | 200+160 −60 ms | α | 253Md | (1/2−) | ||||||||||||||
IT | 257Lr | ||||||||||||||||||
258Lr [15] | 103 | 155 | 258.10176(11)# | 3.54+0.46 −0.36 s | α (97.4%) | 254Md | |||||||||||||
β+ (2.6%) | 258No | ||||||||||||||||||
259Lr [16] | 103 | 156 | 259.10290(8)# | 6.2(3) s | α (78%) | 255Md | 1/2-# | ||||||||||||
SF (22%) | (various) | ||||||||||||||||||
β+ (rare) | 259No | ||||||||||||||||||
260Lr [17] | 103 | 157 | 260.10551(13)# | 3.0(5) min | α (80%) | 256Md | |||||||||||||
β+ (20%) | 260No | ||||||||||||||||||
SF (rare) | (various) | ||||||||||||||||||
261Lr [18] | 103 | 158 | 261.10688(22)# | 39(12) min | SF | (various) | 1/2-# | ||||||||||||
α (<10%) [19] | 257Md | ||||||||||||||||||
262Lr [20] | 103 | 159 | 262.10961(22)# | ~4 h | β+ | 262No | |||||||||||||
SF (<10%) | (various) | ||||||||||||||||||
α (<7.5%) [21] | 258Md | ||||||||||||||||||
264Lr [n 9] | 103 | 161 | 264.11420(47)# | 4.8+2.2 −1.3 h [2] | SF | (various) | |||||||||||||
266Lr [n 10] | 103 | 163 | 266.11983(56)# | 22(14) h [11+21 −5 h] [22] | SF | (various) | |||||||||||||
This table header & footer: |
SF: | Spontaneous fission |
This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Evidence was provided for the formation of 253Lr in the 2n exit channel. In 2022, two states (253Lr and 253mLr) were found.
This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. In 2022, two states (251Lr and 251mLr) were found.
This reaction was reported in 1984 by Yuri Oganessian at the FLNR. The team was able to detect decays of 246Cf, a descendant of 254Lr.
This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Results are not readily available.
This reaction has been used to study the spectroscopic properties of 255Lr. The team at GANIL used the reaction in 2003 and the team at the FLNR used it between 2004–2006 to provide further information for the decay scheme of 255Lr. The work provided evidence for an isomeric level in 255Lr.
This reaction was first studied in 1965 by the team at the FLNR. They were able to detect activity with a characteristic decay of 45 seconds, which was assigned to256Lr or 257Lr. Later work suggests an assignment to 256Lr. Further studies in 1968 produced an 8.35–8.60 MeV alpha activity with a half-life of 35 seconds. This activity was also initially assigned to 256Lr or 257Lr and later to solely 256Lr.
This reaction was studied in 1970 by the team at the FLNR. They were able to detect an 8.38 MeV alpha activity with a half-life of 20s. This was assigned to255Lr.
This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to assign alpha activities to260Lr,259Lr and 258Lr from the 3-5n exit channels.
This reaction was studied in 1988 at the LBNL in order to assess the possibility of producing 262Lr and 261Lr without using the exotic 254Es target. It was also used to attempt to measure an electron capture (EC) branch in 261mRf from the 5n exit channel. After extraction of the Lr(III) component, they were able to measure the spontaneous fission of 261Lr with an improved half-life of 44 minutes. The production cross-section was 700 pb. On this basis, a 14% electron capture branch was calculated if this isotope was produced via the 5n channel rather than the p4n channel. A lower bombarding energy (93 MeV c.f. 97 MeV) was then used to measure the production of 262Lr in the p3n channel. The isotope was successfully detected and a yield of 240 pb was measured. The yield was lower than expected compared to the p4n channel. However, the results were judged to indicate that the 261Lr was most likely produced by a p3n channel and an upper limit of 14% for the electron capture branch of 261mRf was therefore suggested.
This reaction was studied briefly in 1958 at the LBNL using an enriched 244Cm target (5% 246Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25 seconds. Later results suggest a tentative assignment to 257Lr from the 3n channel
This reaction was studied briefly in 1958 at the LBNL using an enriched 244Cm target (5% 246Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25s. Later results suggest a tentative assignment to 257Lr from the 3n channel with the 246Cm component. No activities assigned to reaction with the 244Cm component have been reported.
This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to detect an activity assigned to 260Lr. The reaction was further studied in 1988 to study the aqueous chemistry of lawrencium. A total of 23 alpha decays were measured for 260Lr, with a mean energy of 8.03 MeV and an improved half-life of 2.7 minutes. The calculated cross-section was 8.7 nb.
This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% 252Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to 257Lr. Later results suggest a reassignment to 258Lr, resulting from the 5n exit channel. The 8.4 MeV activity was also assigned to 257Lr. Later results suggest a reassignment to 256Lr. This is most likely from the 33% 250Cf component in the target rather than from the 7n channel. The 8.2 MeV was subsequently associated with nobelium.
This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% 252Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to 257Lr. Later results suggest a reassignment to 258Lr. The 8.4 MeV activity was also assigned to 257Lr. Later results suggest a reassignment to 256Lr. The 8.2 MeV was subsequently associated with nobelium.
This reaction was studied in 1971 at the LBNL. They were able to identify a 0.7s alpha activity with two alpha lines at 8.87 and 8.82 MeV. This was assigned to257Lr.
This reaction was first studied in 1970 at the LBNL in an attempt to study the aqueous chemistry of lawrencium. They were able to measure a Lr3+ activity. The reaction was repeated in 1976 at Oak Ridge and 26s 256Lr was confirmed by measurement of coincident X-rays.
This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activity assigned to 258Lr from the p2n channel.
This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activities assigned to 258Lr and 257Lr from the α2n and α3n and channels. The reaction was repeated in 1976 at Oak Ridge and the synthesis of 258Lr was confirmed.
This reaction was studied in 1987 at the LLNL. They were able to detect new spontaneous fission (SF) activities assigned to 261Lr and 262Lr, resulting from transfer from the 22Ne nuclei to the 254Es target. In addition, a 5 ms SF activity was detected in delayed coincidence with nobelium K-shell X-rays and was assigned to 262No, resulting from the electron capture of 262Lr.
Isotopes of lawrencium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:
Parent nuclide | Observed lawrencium isotope |
---|---|
294Ts, 290Mc, 286Nh, 282Rg, 278Mt, 274Bh, 270Db | 266Lr |
288Mc, 284Nh, 280Rg, 276Mt, 272Bh, 268Db | 264Lr |
267Bh, 263Db | 259Lr |
278Nh, 274Rg, 270Mt, 266Bh, 262Db | 258Lr |
261Db | 257Lr |
272Rg, 268Mt, 264Bh, 260Db | 256Lr |
259Db | 255Lr |
266Mt, 262Bh, 258Db | 254Lr |
261Bh, 257Dbg,m | 253Lrg,m |
260Bh, 256Db | 252Lr |
255Db | 251Lr |
Isotope | Year discovered | discovery reaction |
---|---|---|
251Lrg | 2005 | 209Bi(48Ti,2n) |
251Lrm | 2022 | 203Tl(50Ti,2n) |
252Lr | 2001 | 209Bi(50Ti,3n) |
253Lrg | 1985 | 209Bi(50Ti,2n) |
253Lrm | 2001 | 209Bi(50Ti,2n) |
254Lrg | 1985 | 209Bi(50Ti,n) |
254Lrm | 2019 | |
255Lrg | 1970 | 243Am(16O,4n) |
255Lrm1 | 2006 | |
255Lrm2 | 2009 | |
255Lrm3 | 2008 | |
256Lr | 1961? 1965? 1968? 1971 | 252Cf(10B,6n) |
257Lrg | 1958? 1971 | 249Cf(15N,α3n) |
257Lrm | 2018 | |
258Lr | 1961? 1971 | 249Cf(15N,α2n) |
259Lr | 1971 | 248Cm(15N,4n) |
260Lr | 1971 | 248Cm(15N,3n) |
261Lr | 1987 | 254Es + 22Ne |
262Lr | 1987 | 254Es + 22Ne |
264Lr | 2020 | 243Am(48Ca,6α3n) |
266Lr | 2014 | 249Bk(48Ca,7α3n) |
Fourteen isotopes of lawrencium plus seven isomers have been synthesized with 266Lr being the longest-lived and the heaviest, with a half-life of 11 hours. 251Lr is the lightest isotope of lawrencium to be produced to date.
A study of the decay properties of 257Db (see dubnium) in 2001 by Hessberger et al. at the GSI provided some data for the decay of 253Lr. Analysis of the data indicated the population of an isomeric level in 253Lr from the decay of the corresponding isomer in 257Db. The ground state was assigned spin and parity of 7/2−, decaying by emission of an 8794 keV alpha particle with a half-life of 0.57 s. The isomeric level was assigned spin and parity of 1/2−, decaying by emission of an 8722 keV alpha particle with a half-life of 1.49 s.
Recent work on the spectroscopy of 255Lr formed in the reaction 209Bi(48Ca,2n)255Lr has provided evidence for an isomeric level.
Fluorine (9F) has 18 known isotopes ranging from 13
F
to 31
F
and two isomers. Only fluorine-19 is stable and naturally occurring in more than trace quantities; therefore, fluorine is a monoisotopic and mononuclidic element.
Astatine (85At) has 41 known isotopes, all of which are radioactive; their mass numbers range from 188 to 229. There are also 24 known metastable excited states. The longest-lived isotope is 210At, which has a half-life of 8.1 hours; the longest-lived isotope existing in naturally occurring decay chains is 219At with a half-life of 56 seconds.
There are 42 isotopes of polonium (84Po). They range in size from 186 to 227 nucleons. They are all radioactive. 210Po with a half-life of 138.376 days has the longest half-life of any naturally-occurring isotope of polonium and is the most common isotope of polonium. It is also the most easily synthesized polonium isotope. 209Po, which does not occur naturally, has the longest half-life of all isotopes of polonium at 125.2 years. 209Po can be made by using a cyclotron to bombard bismuth with protons, as can 208Po.
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 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.
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.
Calcium (20Ca) has 26 known isotopes, ranging from 35Ca to 60Ca. There are five stable isotopes, plus one isotope (48Ca) with such a long half-life that for all practical purposes it can be considered stable. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. Calcium also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 99,400 years. Unlike cosmogenic isotopes that are produced in the atmosphere, 41Ca is produced by neutron activation of 40Ca. Most of its production is in the upper metre of the soil column, where the cosmogenic neutron flux is still sufficiently strong. 41Ca has received much attention in stellar studies because it decays to 41K, a critical indicator of solar system anomalies. The most stable artificial radioisotopes are 45Ca with a half-life of 163 days and 47Ca with a half-life of 4.5 days. All other calcium isotopes have half-lives measured in minutes or less.
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.
Magnesium (12Mg) naturally occurs in three stable isotopes: 24
Mg, 25
Mg, and 26
Mg. There are 19 radioisotopes that have been discovered, ranging from 18
Mg to 40
Mg. The longest-lived radioisotope is 28
Mg with a half-life of 20.915(9) h. The lighter isotopes mostly decay to isotopes of sodium while the heavier isotopes decay to isotopes of aluminium. The shortest-lived is proton-unbound 19
Mg with a half-life of 5(3) picoseconds, though the half-life of similarly unbound 18
Mg has not been measured.
Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940. Twenty plutonium radioisotopes have been characterized. The most stable are plutonium-244 with a half-life of 80.8 million years, plutonium-242 with a half-life of 373,300 years, and plutonium-239 with a half-life of 24,110 years. All of the remaining radioactive isotopes have half-lives that are less than 7,000 years. This element also has eight meta states; all have half-lives of less than one second.
Americium (95Am) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no known stable isotopes. The first isotope to be synthesized was 241Am in 1944. The artificial element decays by ejecting alpha particles. Americium has an atomic number of 95. Despite 243
Am being an order of magnitude longer lived than 241
Am, the former is harder to obtain than the latter as more of it is present in spent nuclear fuel.
Californium (98Cf) is an artificial 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 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer, 249mCf. The longest-lived isotope is 251Cf with a half-life of 898 years.
Einsteinium (99Es) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be discovered was 253Es in 1952. There are 18 known radioisotopes from 240Es to 257Es, and 3 nuclear isomers. The longest-lived isotope is 252Es with a half-life of 471.7 days, or around 1.293 years.
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.
Dubnium (105Db) is a synthetic element, thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 261Db in 1968. The 13 known radioisotopes are from 255Db to 270Db, and 1–3 isomers. The longest-lived known isotope is 268Db with a half-life of 16 hours.
Bohrium (107Bh) is an artificial element. Like all artificial elements, it has no stable isotopes, and a standard atomic weight cannot be given. The first isotope to be synthesized was 262Bh in 1981. There are 11 known isotopes ranging from 260Bh to 274Bh, and 1 isomer, 262mBh. The longest-lived isotope is 270Bh with a half-life of 2.4 minutes, although the unconfirmed 278Bh may have an even longer half-life of about 690 seconds.
Hassium (108Hs) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 265Hs in 1984. There are 13 known isotopes from 263Hs to 277Hs and 1–4 isomers. The most stable isotope of hassium cannot be determined based on existing data due to uncertainty that arises from the low number of measurements. The half-lives of 269Hs and 271Hs are about 12 seconds, whereas that of 270Hs is about 7.6 seconds. It is also possible that 277mHs is more stable than these, with its half-life likely being 130±100 seconds, but only one event of decay of this isotope has been registered as of 2016.
Oganesson (118Og) is a synthetic element created in particle accelerators, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first and only isotope to be synthesized was 294Og in 2002 and 2005; it has a half-life of 700 microseconds.
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