Roentgenium Roentgenium is a chemical element with the symbol Rg and atomic number 111. It is an extremely radioactive synthetic element that can be created in a laboratory but is not found in nature. The most stable known isotope, roentgenium-282, has a h ...

(₁₁₁Rg) is a

synthetic element A synthetic element is one of 24 known chemical elements that do not occur naturally on Earth: they have been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; ...

, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no

stable isotope The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...

s. The first

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...

to be synthesized was ²⁷²Rg in 1994, which is also the only directly synthesized isotope; all others are decay products of heavier elements. There are seven known

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s, having mass numbers of 272, 274, and 278–282. The longest-lived isotope is ²⁸²Rg with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

of about 2 minutes, although the unconfirmed ²⁸³Rg and ²⁸⁶Rg may have longer half-lives of about 5.1 minutes and 10.7 minutes respectively.

List of isotopes

, - , ²⁷²Rg , 111 , 161 , 272.15327(25)# , , α , ²⁶⁸Mt , 5+#, 6+# , - , ²⁷⁴RgNot directly synthesized, occurs as a decay product of ²⁷⁸Nh , 111 , 163 , 274.15525(19)# , , α , ²⁷⁰Mt , , - , ²⁷⁸RgNot directly synthesized, occurs as a decay product of ²⁸²Nh , 111 , 167 , 278.16149(38)# , , α , ²⁷⁴Mt , , - , rowspan=2, ²⁷⁹RgNot directly synthesized, occurs in

decay chain In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay dire ...

of ²⁸⁷Mc , rowspan=2, 111 , rowspan=2, 168 , rowspan=2, 279.16272(51)# , rowspan=2, , α (87%) , ²⁷⁵Mt , , - , SF (13%) , (various) , - , rowspan=2, ²⁸⁰RgNot directly synthesized, occurs in decay chain of ²⁸⁸Mc , rowspan=2, 111 , rowspan=2, 169 , rowspan=2, 280.16514(61)# , rowspan=2, , α (87%) , ²⁷⁶Mt , , - , EC (13%) , ²⁸⁰Ds , , - , rowspan=2 , ²⁸¹RgNot directly synthesized, occurs in decay chain of ²⁹³Ts , rowspan=2 , 111 , rowspan=2 , 170 , rowspan=2 , 281.16636(89)# , rowspan=2 , , SF (86%) , (various) , rowspan=2, , - , α (14%) , ²⁷⁷Mt , - , ²⁸²RgNot directly synthesized, occurs in decay chain of ²⁹⁴Ts , 111 , 171 , 282.16912(72)# , , α , ²⁷⁸Mt , , - , ²⁸³RgNot directly synthesized, occurs in decay chain of ²⁸⁷Fl; unconfirmed , 111 , 172 , 283.17054(79)# , 5.1 min? , SF , (various) , , - , ²⁸⁶RgNot directly synthesised, occurs in decay chain of ²⁹⁰Fl and ²⁹⁴Lv; unconfirmed , 111 , 175 , , 10.7 min? , α , ²⁸²Mt ,

Isotopes and nuclear properties

Nucleosynthesis

Super-heavy elements such as roentgenium are produced by bombarding lighter elements in

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

s that induce

fusion reaction Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifeste ...

s. Whereas the lightest isotope of roentgenium, roentgenium-272, can be synthesized directly this way, all the heavier roentgenium isotopes 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 an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...

s. Depending on the energies involved, fusion reactions can be categorized as "hot" or "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (

actinide The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The info ...

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 from rest through an electric potential difference of one volt in vacu ...

) 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 reactions. As the fused nuclei cool to the ground state, they require emission of only one or two neutrons, and thus, allows 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 "hot" fusion that is known to take place naturally within stars and artificially in hydrogen bombs and p ...

). The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=111.

Cold fusion

Before the first successful synthesis of roentgenium in 1994 by the GSI team, a team at the

Joint Institute for Nuclear Research The Joint Institute for Nuclear Research (JINR, russian: Объединённый институт ядерных исследований, ОИЯИ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research c ...

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 one o ...

, Russia, also tried to synthesize roentgenium by bombarding bismuth-209 with nickel-64 in 1986. No roentgenium atoms were identified. After an upgrade of their facilities, the team at GSI successfully detected 3 atoms of ²⁷²Rg in their discovery experiment. A further 3 atoms were synthesized in 2002. The discovery of roentgenium was confirmed in 2003 when a team at RIKEN measured the decays of 14 atoms of ²⁷²Rg. The same roentgenium isotope was also observed by an American team at the Lawrence Berkeley National Laboratory (LBNL) from the reaction: : + → + This reaction was conducted as part of their study of projectiles with odd

in cold fusion reactions. The ²⁰⁵Tl(⁷⁰Zn,n)²⁷⁴Rg reaction was tried by the RIKEN team in 2004 and repeated in 2010 in an attempt to secure the discovery of its parent ²⁷⁸Nh: : + → + Due to the weakness of the thallium target, they were unable to detect any atoms of ²⁷⁴Rg.

As decay product

All the isotopes of roentgenium except roentgenium-272 have been detected only in the decay chains of elements with a higher

, such as

nihonium Nihonium is a synthetic chemical element with the 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 transactinide ...

. Nihonium currently has seven known isotopes; all of them undergo alpha decays to become roentgenium nuclei, with mass numbers between 274 and 286. Parent nihonium nuclei can be themselves decay products of

moscovium Moscovium is a synthetic element with the 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 Research (JINR) in Dubna, Russia. In December 2015, ...

and

tennessine Tennessine is a synthetic chemical element with the symbol Ts and atomic number 117. It is the second-heaviest known element and the penultimate element of the 7th period of the periodic table. The discovery of tennessine was officially anno ...

, and (via unconfirmed branches)

flerovium Flerovium is a Transactinide element, superheavy chemical element with Chemical symbol, symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. It is named after the Flerov Laboratory of Nuclear Reactions of the Joint ...

and

livermorium Livermorium is a synthetic chemical element with the symbol Lv and has an atomic number of 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 afte ...

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

JINR The Joint Institute for Nuclear Research (JINR, russian: Объединённый институт ядерных исследований, ОИЯИ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research ce ...

) identified roentgenium-281 as a final product in the decay of tennessine via an alpha decay sequence: : → + : → + : → +

Nuclear isomerism

;²⁷⁴Rg Two atoms of ²⁷⁴Rg have been observed in the

of ²⁷⁸Nh. They decay by

alpha emission Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...

, emitting alpha particles with different energies, and have different lifetimes. In addition, the two entire decay chains appear to be different. This suggests the presence of two nuclear isomers but further research is required. ;²⁷²Rg Four alpha particles emitted from ²⁷²Rg with energies of 11.37, 11.03, 10.82, and 10.40 MeV have been detected. The GSI measured ²⁷²Rg to have a half-life of 1.6 ms while recent data from RIKEN have given a half-life of 3.8 ms. The conflicting data may be due to nuclear isomers but the current data are insufficient to come to any firm assignments.

Chemical yields of isotopes

Cold fusion

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

Theoretical calculations

Evaporation residue cross sections

The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given. DNS = Di-nuclear system; σ = cross section

References

* Isotope masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** ** {{Navbox element isotopes Roentgenium