Bohrium
Encyclopedia
Bohrium is a chemical element
with the symbol Bh and atomic number
107 and is the heaviest member of group 7 (VIIB).
It is a synthetic element
whose most stable known isotope
, 270Bh, has a half-life
of 61 seconds. Chemical experiments have confirmed bohrium's predicted position as a heavier homologue to rhenium
with the formation of a stable +7 oxidation state
.
and Gottfried Münzenberg
at the Gesellschaft für Schwerionenforschung
(Institute for Heavy Ion Research, GSI) in Darmstadt
using the Dubna reaction.
In 1989, the GSI team successfully repeated the reaction during their efforts to measure an excitation function
. During these experiments, 261Bh was also identified in the 2n evaporation channel and it was confirmed that 262Bh exists as two states - a ground state and an isomeric
state.
The IUPAC/IUPAP Transfermium Working Group report in 1992 officially recognised the GSI team as discoverers of bohrium.
-rhenium
.
The German group suggested the name nielsbohrium with symbol Ns to honor the Danish physicist Niels Bohr
. The Soviet scientists had suggested this name be given to element 105 (which was finally called dubnium
) and the German team wished to recognise both Bohr and the fact that the Dubna team had been the first to propose the cold fusion reaction.
There was an element naming controversy
as to what the elements from 104 to 106 were to be called; the IUPAC adopted unnilseptium (symbol Uns) as a temporary, systematic element name
for this element. In 1994 a committee of IUPAC recommended that element 107 be named bohrium, not nielsbohrium, since there was no precedence for using a scientist's complete name in the naming of an element.
This was opposed by the discoverers who were adamant that they had the right to name the element. The matter was handed to the Danish branch of IUPAC who voted in favour of the name bohrium. There was some concern however that the name might be confused with boron
and in particular the distinguishing of the names of their respective oxo-ions bohrate and borate. Despite this, the name bohrium for element 107 was recognized internationally in 1997. The IUPAC subsequently decided that bohrium salts should be called bohriates.
209Bi(54Cr,xn)263-xBh (x=1,2)
The synthesis of bohrium was first attempted in 1976 by scientists at the Joint Institute for Nuclear Research
at Dubna
using this cold fusion reaction. Analysis was by detection of spontaneous fission
(SF). They discovered two SF activities, one with a 1-2 ms half-life and one with a 5 s activity. Based on the results of other cold fusion reactions, they concluded that they were due to 261Bh and 257Db respectively. However, later evidence gave a much lower SF branching for 261Bh reducing confidence in this assignment. The assignment of the dubnium activity was later changed to 258Db, presuming that the decay of bohrium was missed. The 2 ms SF activity was assigned to 258Rf resulting from the 33% EC
branch.
The GSI team studied the reaction in 1981 in their discovery experiments. Five atoms of 262Bh were detected using the method of correlation of genetic parent-daughter decays.
In 1987, an internal report from Dubna indicated that the team had been able to detect the spontaneous fission
of 261Bh directly.
The GSI team further studied the reaction in 1989 and discovered the new isotope 261Bh during the measurement of the 1n and 2n excitation functions but were unable to detect an SF branching for 261Bh.
They continued their study in 2003 using newly developed bismuth(III) fluoride (BiF3) targets, used to provide further data on the decay data for 262Bh and the daughter 258Db.
The 1n excitation function was remeasured in 2005 by the team at LBNL after some doubt about the accuracy of previous data. They observed 18 atoms of 262Bh and 3 atoms of 261Bh and confirmed the two isomers of 262Bh.
209Bi(53Cr,xn)262-xBh
The team at Dubna studied this reaction in 1976 in order to assist in their assignments of the SF activities from their experiments with a Cr-54 beam. They were unable to detect any such activity, indicating the formation of different isotopes decaying primarily by alpha decay.
209Bi(52Cr,xn)261-xBh (x=1)
This reaction was studied for the first time in 2007 by the team at LBNL to search for the lightest bohrium isotope 260Bh. The team successfully detected 8 atoms of 260Bh decaying by correlated 10.16 MeV alpha particle emission to 256Db. The alpha decay energy indicates the continued stabilising effect of the N=152 closed shell.
208Pb(55Mn,xn)263-xBh (x=1)
The team at Dubna also studied this reaction in 1976 as part of their newly established cold fusion approach to new elements. As for the reaction using a Bi-209 target, they observed the same SF activities and assigned them to 261107 and 257105. Later evidence indicated that these should be reassigned to 258105 and 258104 (see above).
In 1983, they repeated the experiment using a new technique: measurement of alpha decay from a descendant using chemical separation. The team were able to detect the alpha decay from a descendant of the 1n evaporation channel, providing some evidence for the formation of element 107 nuclei.
This reaction was later studied in detail using modern techniques by the team at LBNL. In 2005 they measured 33 decays of 262Bh and 2 atoms of 261Bh, providing a 1n excitation function and some spectroscopic data of both 262Bh isomers. The 2n excitation function was further studied in a 2006 repeat of the reaction.
The team found that this reaction had a higher 1n cross section than the corresponding reaction with a Bi-209 target, contrary to expectations. Further research is required to understand the reasons.
238Am(31P,xn)269-xBh (x=5?)
This reaction was first studied in 2006 at the LBNL as part of their systematic study of fusion reactions using 238U targets. Results have not been published but preliminary results appear to indicate the observation of spontaneous fission
, possibly from 264Bh.
243Am(26Mg,xn)269-xBh (x=3,4,5)
Recently, the team at the Institute of Modern Physics (IMP), Lanzhou, have studied the nuclear reaction between americium-243 and magnesium-26 ions in order to synthesise the new isotope 265Bh
and gather more data on 266Bh. In two series of experiments, the team has measured partial excitation functions of the 3n,4n and 5n evaporation channels.
248Cm(23Na,xn)271-xBh (x=4,5)
This reaction was studied for the first time in 2008 by the team at RIKEN, Japan, in order to study the decay properties of 266Bh, which is a decay product in their claimed decay chains of ununtrium
. The decay of 266Bh by the emission of 9.05-9.23 MeV alpha particles was further confirmed in 2010.
249Bk(22Ne,xn)271-xBh (x=4)
The first attempts to synthesize bohrium by hot fusion pathways were performed in 1979 by the team at Dubna. The reaction was repeated in 1983. In both cases, they were unable to detect any spontaneous fission
from nuclei of bohrium.
More recently, hot fusions pathways to bohrium have been re-investigated in order to allow for the synthesis of more long-lived, neutron
rich isotopes to allow a first chemical study of bohrium. In 1999, the team at LBNL claimed the discovery of long-lived 267Bh (5 atoms) and 266Bh (1 atom). Later, both of these were confirmed. The team at the Paul Scherrer Institute (PSI) in Bern, Switzerland later synthesized 6 atoms of 267Bh in the first definitive study of the chemistry of bohrium (see below).
254Es(16O,xn)270-xBh
As an alternative means of producing long-lived bohrium isotopes suitable for a chemical study, the synthesis of 267Bh and 266Bh were attempted in 1995 by the team at GSI using the highly asymmetric reaction using an einsteinium-254 target. They were unable to detect any product atoms.
is theoretically possible, though highly unlikely.
The only confirmed example of isomerism in bohrium is for the isotope 262Bh. Direct production populates two states, a ground state and an isomeric state. The ground state is confirmed as decaying by alpha emission with alpha lines at 10.08,9.82 and 9.76 MeV with a revised half-life of 84 ms. The excited state decays by alpha emission with lines at 10.37 and 10.24 MeV with a revised half-life of 9.6 ms.
, technetium
and rhenium
. All the members of the group readily portray their group oxidation state of +7 and the state becomes more stable as the group is descended. Thus bohrium is expected to form a stable +7 state. Technetium also shows a stable +4 state whilst rhenium exhibits stable +4 and +3 states. Bohrium may therefore show these lower states as well.
The heavier members of the group are known to form volatile heptoxides M2O7, so bohrium should also form the volatile oxide Bh2O7. The oxide should dissolve in water to form perbohric acid, HBhO4.
Rhenium and technetium form a range of oxyhalides from the halogenation of the oxide. The chlorination of the oxide forms the oxychlorides MO3Cl, so BhO3Cl should be formed in this reaction. Fluorination results in MO3F and MO2F3 for the heavier elements in addition to the rhenium compounds ReOF5 and ReF7. Therefore, oxyfluoride formation for bohrium may help to indicate eka-rhenium properties.
In 2000, it was confirmed that although relativistic effects are important, the 107-th element does behave like a typical group 7 element
.
In 2000, a team at the PSI conducted a chemistry reaction using atoms of 267Bh produced in the reaction between Bk-249 and Ne-22 ions. The resulting atoms were thermalised and reacted with a HCl/O2 mixture to form a volatile oxychloride. The reaction also produced isotopes of its lighter homologues, technetium
(as 108Tc) and rhenium
(as 169Re). The isothermal adsorption curves were measured and gave strong evidence for the formation of a volatile oxychloride with properties similar to that of rhenium oxychloride. This placed bohrium as a typical member of group 7.
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with the symbol Bh and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
107 and is the heaviest member of group 7 (VIIB).
It is a synthetic element
Synthetic element
In chemistry, a synthetic element is a chemical element that is too unstable to occur naturally on Earth, and therefore has to be created artificially. So far 30 synthetic elements have been discovered—that is, synthesized...
whose most stable known isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
, 270Bh, has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 61 seconds. Chemical experiments have confirmed bohrium's predicted position as a heavier homologue to rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
with the formation of a stable +7 oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
.
Official discovery
The first convincing synthesis was in 1981 by a German research team led by Peter ArmbrusterPeter Armbruster
Peter Armbruster is a physicist at the Gesellschaft für Schwerionenforschung facility in Darmstadt, Germany, and is credited with co-discovering elements 107 , 108 , 109 , 110 , 111 , and 112 with research partner Gottfried Münzenberg.He studied physics at the Technical...
and Gottfried Münzenberg
Gottfried Münzenberg
Gottfried Münzenberg is a German physicist.He studied physics at Justus-Liebig-Universität in Giessen and Leopold-Franzens-Universität Innsbruck and completed his studies with a Ph.D. at the University of Giessen, Germany, in 1971...
at the Gesellschaft für Schwerionenforschung
Gesellschaft für Schwerionenforschung
The GSI Helmholtz Centre for Heavy Ion Research GmbH in the Wixhausen suburb of Darmstadt, Germany is a federally and state co-funded heavy ion research center. The current director of GSI is Horst Stöcker who succeeded Walter F...
(Institute for Heavy Ion Research, GSI) in Darmstadt
Darmstadt
Darmstadt is a city in the Bundesland of Hesse in Germany, located in the southern part of the Rhine Main Area.The sandy soils in the Darmstadt area, ill-suited for agriculture in times before industrial fertilisation, prevented any larger settlement from developing, until the city became the seat...
using the Dubna reaction.
- + → +
In 1989, the GSI team successfully repeated the reaction during their efforts to measure an excitation function
Excitation function
Excitation function is a term used in nuclear physics to describe a graphical plot of the yield of a radionuclide or reaction channel as a function of the bombarding projectile energy or the calculated excitation energy of the compound nucleus....
. During these experiments, 261Bh was also identified in the 2n evaporation channel and it was confirmed that 262Bh exists as two states - a ground state and an isomeric
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
state.
The IUPAC/IUPAP Transfermium Working Group report in 1992 officially recognised the GSI team as discoverers of bohrium.
Proposed names
Historically bohrium has been referred to as ekaMendeleev's predicted elements
Professor Dmitri Mendeleev published the first Periodic Table of the Atomic Elements in 1869 based on properties which appeared with some regularity as he laid out the elements from lightest to heaviest....
-rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
.
The German group suggested the name nielsbohrium with symbol Ns to honor the Danish physicist Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
. The Soviet scientists had suggested this name be given to element 105 (which was finally called dubnium
Dubnium
The Soviet team proposed the name nielsbohrium in honor of the Danish nuclear physicist Niels Bohr. The American team proposed that the new element should be named hahnium , in honor of the late German chemist Otto Hahn...
) and the German team wished to recognise both Bohr and the fact that the Dubna team had been the first to propose the cold fusion reaction.
There was an element naming controversy
Element naming controversy
The names for the chemical elements 104 to 106 were the subject of a major controversy starting in the 1960s, described by some nuclear chemists as the Transfermium Wars because it concerned the elements following fermium on the periodic table....
as to what the elements from 104 to 106 were to be called; the IUPAC adopted unnilseptium (symbol Uns) as a temporary, systematic element name
Systematic element name
A systematic element name is the temporary name and symbol assigned to newly synthesized and not yet synthesized chemical elements. In chemistry, a transuranic element receives a permanent name and symbol only after its synthesis has been confirmed. In some cases, this has been a protracted and...
for this element. In 1994 a committee of IUPAC recommended that element 107 be named bohrium, not nielsbohrium, since there was no precedence for using a scientist's complete name in the naming of an element.
This was opposed by the discoverers who were adamant that they had the right to name the element. The matter was handed to the Danish branch of IUPAC who voted in favour of the name bohrium. There was some concern however that the name might be confused with boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
and in particular the distinguishing of the names of their respective oxo-ions bohrate and borate. Despite this, the name bohrium for element 107 was recognized internationally in 1997. The IUPAC subsequently decided that bohrium salts should be called bohriates.
Cold fusion
This section deals with the synthesis of nuclei of bohrium by so-called "cold" fusion reactions. These are processes which create compound nuclei at low excitation energy (~10-20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.209Bi(54Cr,xn)263-xBh (x=1,2)
The synthesis of bohrium was first attempted in 1976 by scientists at the Joint Institute for Nuclear Research
Joint Institute for Nuclear Research
The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow Oblast , Russia, is an international research centre for nuclear sciences, with 5500 staff members, 1200 researchers including 1000 Ph.D.s from eighteen member states The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow...
at Dubna
Dubna
Dubna is a town in Moscow Oblast, Russia. It has a status of naukograd , being home to the Joint Institute for Nuclear Research, an international nuclear physics research centre and one of the largest scientific foundations in the country. It is also home to MKB Raduga, a defence aerospace company...
using this cold fusion reaction. Analysis was by detection of spontaneous fission
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
(SF). They discovered two SF activities, one with a 1-2 ms half-life and one with a 5 s activity. Based on the results of other cold fusion reactions, they concluded that they were due to 261Bh and 257Db respectively. However, later evidence gave a much lower SF branching for 261Bh reducing confidence in this assignment. The assignment of the dubnium activity was later changed to 258Db, presuming that the decay of bohrium was missed. The 2 ms SF activity was assigned to 258Rf resulting from the 33% EC
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
branch.
The GSI team studied the reaction in 1981 in their discovery experiments. Five atoms of 262Bh were detected using the method of correlation of genetic parent-daughter decays.
In 1987, an internal report from Dubna indicated that the team had been able to detect the spontaneous fission
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
of 261Bh directly.
The GSI team further studied the reaction in 1989 and discovered the new isotope 261Bh during the measurement of the 1n and 2n excitation functions but were unable to detect an SF branching for 261Bh.
They continued their study in 2003 using newly developed bismuth(III) fluoride (BiF3) targets, used to provide further data on the decay data for 262Bh and the daughter 258Db.
The 1n excitation function was remeasured in 2005 by the team at LBNL after some doubt about the accuracy of previous data. They observed 18 atoms of 262Bh and 3 atoms of 261Bh and confirmed the two isomers of 262Bh.
209Bi(53Cr,xn)262-xBh
The team at Dubna studied this reaction in 1976 in order to assist in their assignments of the SF activities from their experiments with a Cr-54 beam. They were unable to detect any such activity, indicating the formation of different isotopes decaying primarily by alpha decay.
209Bi(52Cr,xn)261-xBh (x=1)
This reaction was studied for the first time in 2007 by the team at LBNL to search for the lightest bohrium isotope 260Bh. The team successfully detected 8 atoms of 260Bh decaying by correlated 10.16 MeV alpha particle emission to 256Db. The alpha decay energy indicates the continued stabilising effect of the N=152 closed shell.
208Pb(55Mn,xn)263-xBh (x=1)
The team at Dubna also studied this reaction in 1976 as part of their newly established cold fusion approach to new elements. As for the reaction using a Bi-209 target, they observed the same SF activities and assigned them to 261107 and 257105. Later evidence indicated that these should be reassigned to 258105 and 258104 (see above).
In 1983, they repeated the experiment using a new technique: measurement of alpha decay from a descendant using chemical separation. The team were able to detect the alpha decay from a descendant of the 1n evaporation channel, providing some evidence for the formation of element 107 nuclei.
This reaction was later studied in detail using modern techniques by the team at LBNL. In 2005 they measured 33 decays of 262Bh and 2 atoms of 261Bh, providing a 1n excitation function and some spectroscopic data of both 262Bh isomers. The 2n excitation function was further studied in a 2006 repeat of the reaction.
The team found that this reaction had a higher 1n cross section than the corresponding reaction with a Bi-209 target, contrary to expectations. Further research is required to understand the reasons.
Hot fusion
This section deals with the synthesis of nuclei of bohrium by so-called "hot" fusion reactions. These are processes which create compound nuclei at high excitation energy (~40-50 MeV, hence "hot"), leading to a reduced probability of survival from fission and quasi-fission. The excited nucleus then decays to the ground state via the emission of 3-5 neutrons.238Am(31P,xn)269-xBh (x=5?)
This reaction was first studied in 2006 at the LBNL as part of their systematic study of fusion reactions using 238U targets. Results have not been published but preliminary results appear to indicate the observation of spontaneous fission
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
, possibly from 264Bh.
243Am(26Mg,xn)269-xBh (x=3,4,5)
Recently, the team at the Institute of Modern Physics (IMP), Lanzhou, have studied the nuclear reaction between americium-243 and magnesium-26 ions in order to synthesise the new isotope 265Bh
and gather more data on 266Bh. In two series of experiments, the team has measured partial excitation functions of the 3n,4n and 5n evaporation channels.
248Cm(23Na,xn)271-xBh (x=4,5)
This reaction was studied for the first time in 2008 by the team at RIKEN, Japan, in order to study the decay properties of 266Bh, which is a decay product in their claimed decay chains of ununtrium
Ununtrium
Ununtrium is the temporary name of a synthetic element with the temporary symbol Uut and atomic number 113.It is placed as the heaviest member of the group 13 elements although a sufficiently stable isotope is not known at this time that would allow chemical experiments to confirm its position...
. The decay of 266Bh by the emission of 9.05-9.23 MeV alpha particles was further confirmed in 2010.
249Bk(22Ne,xn)271-xBh (x=4)
The first attempts to synthesize bohrium by hot fusion pathways were performed in 1979 by the team at Dubna. The reaction was repeated in 1983. In both cases, they were unable to detect any spontaneous fission
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
from nuclei of bohrium.
More recently, hot fusions pathways to bohrium have been re-investigated in order to allow for the synthesis of more long-lived, neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
rich isotopes to allow a first chemical study of bohrium. In 1999, the team at LBNL claimed the discovery of long-lived 267Bh (5 atoms) and 266Bh (1 atom). Later, both of these were confirmed. The team at the Paul Scherrer Institute (PSI) in Bern, Switzerland later synthesized 6 atoms of 267Bh in the first definitive study of the chemistry of bohrium (see below).
254Es(16O,xn)270-xBh
As an alternative means of producing long-lived bohrium isotopes suitable for a chemical study, the synthesis of 267Bh and 266Bh were attempted in 1995 by the team at GSI using the highly asymmetric reaction using an einsteinium-254 target. They were unable to detect any product atoms.
As decay products
Isotopes of bohrium have also been detected in the decay of heavier elements. Observations to date are shown in the table below:| Evaporation Residue | Observed Bh isotope |
|---|---|
| 294Uus | 274Bh |
| 288Uup | 272Bh |
| 287Uup | 271Bh |
| 282Uut | 270Bh |
| 278Uut | 266Bh |
| 272Rg | 264Bh |
| 266Mt | 262Bh |
Occurrence
The occurrence of bohrium in nature in such minerals as molybdeniteMolybdenite
Molybdenite is a mineral of molybdenum disulfide, MoS2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum atoms sandwiched between sheets of sulfur atoms...
is theoretically possible, though highly unlikely.
Isotopes
A total of eleven isotopes of bohrium have been characterized. The proton-rich isotopes with masses 260, 261, and 262 were directly produced by cold fusion, those with mass 262 and 264 were reported in the chains of the elements 109 and 111, while the neutron-rich isotopes with masses 266, 267 were created in irradiations of actinide targets. The four most neutron-rich ones with masses 270, 271, 272, and 274 appear in decay chains of 282113, 287115, 288115, and 294117 respectively. These ten isotopes have half-lives ranging from 8 miliseconds to 0.9 minute, and all undergo alpha-decay.| Isotope | Year discovered | discovery reaction | Half-times |
|---|---|---|---|
| 260Bh | 2007 | 209Bi(52Cr,n) | |
| 261Bh | 1989 | 209Bi(54Cr,2n) | |
| 262Bhg,m | 1981 | 209Bi(54Cr,n) | |
| 263Bh | unknown | — | — |
| 264Bh | 1994 | 209Bi(64Ni,n) | |
| 265Bh | 2004 | 243Am(26Mg,4n) | |
| 266Bh | 2000 | |
|
| 267Bh | 2000 | 249Bk(22Ne,4n) | |
| 268Bh | unknown | — | — |
| 269Bh | unknown | — | — |
| 270Bh | 2006 | 237Np(48Ca,3n) see ununtrium Ununtrium Ununtrium is the temporary name of a synthetic element with the temporary symbol Uut and atomic number 113.It is placed as the heaviest member of the group 13 elements although a sufficiently stable isotope is not known at this time that would allow chemical experiments to confirm its position... |
|
| 271Bh | 2005? | 243Am(48Ca,4n) | (5 sec) |
| 272Bh | 2005 | 243Am(48Ca,3n) | 9.8 sec |
| 273Bh | unknown | — | — |
| 274Bh | 2010 | 249Bk(48Ca,3n) | ~54 sec |
Nuclear isomerism
262BhThe only confirmed example of isomerism in bohrium is for the isotope 262Bh. Direct production populates two states, a ground state and an isomeric state. The ground state is confirmed as decaying by alpha emission with alpha lines at 10.08,9.82 and 9.76 MeV with a revised half-life of 84 ms. The excited state decays by alpha emission with lines at 10.37 and 10.24 MeV with a revised half-life of 9.6 ms.
Extrapolated
Bohrium is projected to be the fourth member of the 6d series of transition metals and the heaviest member of group VII in the Periodic Table, below manganeseManganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
, technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
and rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
. All the members of the group readily portray their group oxidation state of +7 and the state becomes more stable as the group is descended. Thus bohrium is expected to form a stable +7 state. Technetium also shows a stable +4 state whilst rhenium exhibits stable +4 and +3 states. Bohrium may therefore show these lower states as well.
The heavier members of the group are known to form volatile heptoxides M2O7, so bohrium should also form the volatile oxide Bh2O7. The oxide should dissolve in water to form perbohric acid, HBhO4.
Rhenium and technetium form a range of oxyhalides from the halogenation of the oxide. The chlorination of the oxide forms the oxychlorides MO3Cl, so BhO3Cl should be formed in this reaction. Fluorination results in MO3F and MO2F3 for the heavier elements in addition to the rhenium compounds ReOF5 and ReF7. Therefore, oxyfluoride formation for bohrium may help to indicate eka-rhenium properties.
Experimental
In 1995, the first report on attempted isolation of the element was unsuccessful.In 2000, it was confirmed that although relativistic effects are important, the 107-th element does behave like a typical group 7 element
Group 7 element
A Group 7 element is one in the series of elements in group 7 in the periodic table, which consists of manganese , technetium , rhenium , and bohrium...
.
In 2000, a team at the PSI conducted a chemistry reaction using atoms of 267Bh produced in the reaction between Bk-249 and Ne-22 ions. The resulting atoms were thermalised and reacted with a HCl/O2 mixture to form a volatile oxychloride. The reaction also produced isotopes of its lighter homologues, technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
(as 108Tc) and rhenium
Rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an average concentration of 1 part per billion , rhenium is one of the rarest elements in the Earth's crust. The free element has...
(as 169Re). The isothermal adsorption curves were measured and gave strong evidence for the formation of a volatile oxychloride with properties similar to that of rhenium oxychloride. This placed bohrium as a typical member of group 7.
- 2 Bh + 3 + 2 HCl → 2 +
| Formula | Name(s) |
|---|---|
| BhO3Cl | bohrium oxychloride ; bohrium(VII) chloride trioxide |