Bohrium Bohrium is a synthetic chemical element; it has symbol Bh and atomic number 107. It is named after Danish physicist Niels Bohr. As a synthetic element, it can be created in particle accelerators but is not found in nature. All known isotopes of ...

(₁₀₇Bh) is an

artificial element A synthetic element is a known chemical element that does not occur naturally on Earth: it has been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; thus, it i ...

. Like all artificial elements, it has no

stable isotope Stable nuclides are Isotope, isotopes of a chemical element whose Nucleon, nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The Atomic nucleus, nuclei of such isotopes are no ...

s, and a

standard atomic weight The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, ...

cannot be given. The first

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

to be synthesized was ²⁶²Bh in 1981. There are 11 known isotopes ranging from ²⁶⁰Bh to ²⁷⁴Bh, and 1

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

, ^262mBh. The longest-lived isotope is ²⁷⁰Bh with a

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of 2.4 minutes, although the unconfirmed ²⁷⁸Bh may have an even longer half-life of about 11.5 minutes.

List of isotopes

, -id=Bohrium-260 , ²⁶⁰Bh , style="text-align:right" , 107 , style="text-align:right" , 153 , 260.12144(21)# ,
[] , alpha decay, α , ²⁵⁶Db , , -id=Bohrium-261 , rowspan=2, ²⁶¹Bh , rowspan=2 style="text-align:right" , 107 , rowspan=2 style="text-align:right" , 154 , rowspan=2, 261.12140(19) , rowspan=2,
[] , α , ²⁵⁷Db , rowspan=2, (5/2−) , - , Spontaneous fission, SF (rare) , (various) , -id=Bohrium-262 , rowspan=2, ²⁶²Bh , rowspan=2 style="text-align:right" , 107 , rowspan=2 style="text-align:right" , 155 , rowspan=2, 262.12265(10) , rowspan=2, , α (>80%) , ²⁵⁸Db , rowspan=2, , - , SF (<20%) , (various) , -id=Bohrium-262m , style="text-indent:1em" , ^262mBh , colspan="3" style="text-indent:2em" , 220(50) keV , , α , ²⁵⁸Db , , -id=Bohrium-264 , rowspan=2, ²⁶⁴Bh , rowspan=2 style="text-align:right" , 107 , rowspan=2 style="text-align:right" , 157 , rowspan=2, 264.12449(19)# , rowspan=2, , α (86%) , ²⁶⁰Db , rowspan=2, , - , SF (14%) , (various) , -id=Bohrium-265 , ²⁶⁵Bh , style="text-align:right" , 107 , style="text-align:right" , 158 , 265.12496(26)# ,
[] , α , ²⁶¹Db , , -id=Bohrium-266 , rowspan=2, ²⁶⁶Bh , rowspan=2 style="text-align:right" , 107 , rowspan=2 style="text-align:right" , 159 , rowspan=2, 266.12679(18)# , rowspan=2, , α , ²⁶²Db , rowspan=2, , - , β⁺? , ²⁶⁶Sg , -id=Bohrium-267 , ²⁶⁷Bh , style="text-align:right" , 107 , style="text-align:right" , 160 , 267.12750(28)# ,
[] , α , ²⁶³Db , , -id=Bohrium-270 , ²⁷⁰BhNot directly synthesized, occurs in decay chain of ²⁸²Nh , style="text-align:right" , 107 , style="text-align:right" , 163 , 270.13337(32)# , , α , ²⁶⁶Db , , -id=Bohrium-271 , ²⁷¹BhNot directly synthesized, occurs in decay chain of ²⁸⁷Mc , style="text-align:right" , 107 , style="text-align:right" , 164 , 271.13512(41)# , , α , ²⁶⁷Db , , -id=Bohrium-272 , ²⁷²BhNot directly synthesized, occurs in decay chain of ²⁸⁸Mc , style="text-align:right" , 107 , style="text-align:right" , 165 , 272.13826(57)# , , α , ²⁶⁸Db , , -id=Bohrium-274 , ²⁷⁴BhNot directly synthesized, occurs in decay chain of ²⁹⁴Ts , style="text-align:right" , 107 , style="text-align:right" , 167 , 274.14360(62)# ,
[] , α , ²⁷⁰Db , , -id=Bohrium-278 , ²⁷⁸BhNot directly synthesized, occurs in decay chain of ²⁹⁰Fl and ²⁹⁴Lv; unconfirmed , style="text-align:right" , 107 , style="text-align:right" , 171 , 278.15499(43)# , ? , SF , (various) ,

Nucleosynthesis

Superheavy element Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. The superheavy elements are those beyond the actinides in ...

s such as bohrium are produced by bombarding lighter elements in

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental ...

s that induce

fusion reaction Nuclear fusion is a reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutron by-products. The difference in mass between the reactants and products is manifested as either the release or absorption of energy ...

s. Whereas most of the isotopes of bohrium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of pro ...

s. Depending on the energies involved, the former are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (

actinide The actinide () or actinoid () series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part ...

s), giving rise to compound nuclei at high excitation energy (~40–50−

MeV In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum. When us ...

) that may either fission or evaporate several (3 to 5) neutrons. In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20 MeV), which decreases the probability that these products will undergo fission. As the fused nuclei cool to the

ground state The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state ...

, they require emission of only one or two neutrons, thus allowing for the generation of more neutron-rich products. The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see

cold fusion Cold fusion is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. It would contrast starkly with the nuclear fusion, "hot" fusion that is known to take place naturally within Main sequence, stars and artific ...

). The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with ''Z'' = 107.

Cold fusion

Before the first successful synthesis of hassium in 1981 by the GSI team, the synthesis of bohrium was first attempted in 1976 by scientists at the

Joint Institute for Nuclear Research The Joint Institute for Nuclear Research (JINR, ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research center for nuclear sciences, with 5,500 staff members including 1,200 researchers holding over 1,000 ...

Dubna Dubna ( rus, Дубна́, p=dʊbˈna) is a town in Moscow Oblast, Russia. It has a status of '' naukograd'' (i.e. town of science), being home to the Joint Institute for Nuclear Research, an international nuclear physics research center and o ...

using this cold fusion reaction. They detected two

spontaneous fission Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic proc ...

activities, one with a

of 1–2 ms and one with a half-life of 5 s. 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

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 the

Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory (LBNL, Berkeley Lab) is a Federally funded research and development centers, federally funded research and development center in the Berkeley Hills, hills of Berkeley, California, United States. Established i ...

(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. In 2007, the team at LBNL studied the analogous reaction with chromium-52 projectiles for the first time to search for the lightest bohrium isotope ²⁶⁰Bh: : + → + The team successfully detected 8 atoms of ²⁶⁰Bh decaying by

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...

to ²⁵⁶Db, emitting alpha particles with energy 10.16

. The alpha decay energy indicates the continued stabilizing effect of the N=152 closed shell. The team at Dubna also studied the reaction between lead-208 targets and manganese-55 projectiles in 1976 as part of their newly established cold fusion approach to new elements: : + → + They observed the same spontaneous fission activities as those observed in the reaction between bismuth-209 and chromium-54 and again assigned them to ²⁶¹Bh and ²⁵⁷Db. Later evidence indicated that these should be reassigned to ²⁵⁸Db and ²⁵⁸Rf (see above). In 1983, they repeated the experiment using a new technique: measurement of alpha decay from a

decay product In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( d ...

that had been separated out chemically. The team were able to detect the alpha decay from a decay product of ²⁶²Bh, providing some evidence for the formation of bohrium 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 an excitation function for the reaction emitting one

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

and some spectroscopic data of both ²⁶²Bh isomers. The excitation function for the reaction emitting two neutrons was further studied in a 2006 repeat of the reaction. The team found that the reaction emitting one neutron had a higher

cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture and engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **A ...

than the corresponding reaction with a ²⁰⁹Bi target, contrary to expectations. Further research is required to understand the reasons.

Hot fusion

The reaction between

uranium-238 Uranium-238 ( or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it i ...

targets and

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

-31 projectiles was first studied in 2006 at the LBNL as part of their systematic study of fusion reactions using uranium-238 targets: : + → + 5 Results have not been published but preliminary results appear to indicate the observation of

, possibly from ²⁶⁴Bh. In 2004, the team at the Institute of Modern Physics (IMP),

Lanzhou Lanzhou is the capital and largest city of Gansu province in northwestern China. Located on the banks of the Yellow River, it is a key regional transportation hub, connecting areas further west by rail to the eastern half of the country. His ...

, have studied the nuclear reaction between americium-243 targets and accelerated nuclei of

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

-26 in order to synthesise the new isotope ²⁶⁵Bh and gather more data on ²⁶⁶Bh: : + → + x (x = 3, 4, or 5) In two series of experiments, the team measured partial excitation functions for the reactions emitting three, four, and five neutrons. The reaction between targets of

curium Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inten ...

-248 and accelerated nuclei of

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

-23 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

nihonium Nihonium is a synthetic chemical element; it has symbol Nh and atomic number 113. It is extremely radioactive: its most stable known isotope, nihonium-286, has a half-life of about 10 seconds. In the periodic table, nihonium is a transactini ...

: : + → + x (x = 4 or 5) The decay of ²⁶⁶Bh by the emission of alpha particles with energies of 9.05–9.23 MeV was further confirmed in 2010. The first attempts to synthesize bohrium by hot fusion pathways were performed in 1979 by the team at Dubna, using the reaction between accelerated nuclei of

neon Neon is a chemical element; it has symbol Ne and atomic number 10. It is the second noble gas in the periodic table. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with approximately two-thirds the density of ...

-22 and targets of

berkelium Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National ...

-249: : + → + x (x = 4 or 5) The reaction was repeated in 1983. In both cases, they were unable to detect any

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,

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 The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the Ri ...

(PSI) in

Bern Bern (), or Berne (), ; ; ; . is the ''de facto'' Capital city, capital of Switzerland, referred to as the "federal city".; ; ; . According to the Swiss constitution, the Swiss Confederation intentionally has no "capital", but Bern has gov ...

, Switzerland later synthesized 6 atoms of ²⁶⁷Bh in the first definitive study of the chemistry of bohrium."Gas chemical investigation of bohrium (Bh, element 107)"
, Eichler et al., ''GSI Annual Report 2000''. Retrieved on 2008-02-29

As decay products

Bohrium has been detected in the decay chains of elements with a higher

, such as

meitnerium Meitnerium is a synthetic chemical element; it has symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature, but can be created in a laboratory). The most stable known isotope, meitnerium ...

. Meitnerium currently has seven isotopes that are known to undergo alpha decays to become bohrium nuclei, with mass numbers between 262 and 274. Parent meitnerium nuclei can be themselves decay products of

roentgenium Roentgenium () is a synthetic chemical element; it has symbol Rg and atomic number 111. It is extremely radioactive and can only be created in a laboratory. The most stable known isotope, roentgenium-282, has a half-life of 130 seconds, althoug ...

flerovium Flerovium is a synthetic chemical element; it has symbol Fl and atomic number 114. It is an extremely radioactive, superheavy element, named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Du ...

moscovium Moscovium is a synthetic element, synthetic chemical element; it has Chemical symbol, symbol Mc and atomic number 115. It was first synthesized in 2003 by a joint team of Russian and American scientists at the Joint Institute for Nuclear Resea ...

livermorium Livermorium is a synthetic chemical element; it has symbol Lv and atomic number 116. It is an extremely radioactive element that has only been created in a laboratory setting and has not been observed in nature. The element is named after the La ...

, or

tennessine Tennessine is a synthetic element; it has Chemical symbol, symbol Ts and atomic number 117. It has the second-highest atomic number and joint-highest atomic mass of all known elements and is the penultimate element of the Period 7 element, 7th ...

. For example, in January 2010, the Dubna team (

JINR The Joint Institute for Nuclear Research (JINR, ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research center for nuclear sciences, with 5,500 staff members including 1,200 researchers holding over 1,000 ...

) identified bohrium-274 as a product in the decay of tennessine via an alpha decay sequence: : → + : → + : → + : → + : → +

Nuclear isomerism

;²⁶²Bh The only confirmed example of isomerism in bohrium is in the isotope ²⁶²Bh. Direct synthesis of ²⁶²Bh results in two states, a

and an isomeric state. The ground state is confirmed to decay by alpha decay, emitting alpha particles with energies of 10.08, 9.82, and 9.76 MeV, and has a revised half-life of 84 ms. The excited state also decays by alpha decay, emitting alpha particles with energies of 10.37 and 10.24 MeV, and has a revised half-life of 9.6 ms.

Chemical yields of isotopes

Cold fusion

The table below provides cross-sections and excitation energies for cold fusion reactions producing bohrium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing bohrium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

References

* Half-life, spin, and isomer data selected from the following sources. ** ** ** ** ** ** {{Navbox element isotopes Bohrium