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Island of stability

Island of stability

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The island of stability in nuclear physics
Nuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...

 describes a set of as-yet undiscovered 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...

s of transuranium element
Transuranium element
In chemistry, transuranium elements are the chemical elements with atomic numbers greater than 92...

s which are theorized to be much more stable than others. Specifically, they are expected to have radioactive decay
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...

 half-lives
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 at least minutes or days as compared to seconds, with some expecting half-lives of millions of years.

Theory and origin


The possibility of an "island of stability" was first proposed by Glenn T. Seaborg
Glenn T. Seaborg
Glenn Theodore Seaborg was an American scientist who won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements", contributed to the discovery and isolation of ten elements, and developed the actinide concept, which led to the current arrangement of the...

. The hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

 is that the atomic nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 is built up in "shells" in a manner similar to the structure of the much larger electron shells in atoms. In both cases, shells are just groups of quantum energy level
Energy level
A quantum mechanical system or particle that is bound -- that is, confined spatially—can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy levels...

s that are relatively close to each other. The word "shell" may be further misleading in that it suggests a spherical distribution of electrons when, in fact, the shape of the so-called "shell" may be represented by a symmetrically distorted space resembling, for instance, a 3-dimensional figure-8. Energy levels from quantum states in two different shells will be separated by a relatively large energy gap. So when the number of 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...

s and proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s completely fills the energy level
Energy level
A quantum mechanical system or particle that is bound -- that is, confined spatially—can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy levels...

s of a given shell in the nucleus, the binding energy
Binding energy
Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together—often this means that energy is released upon the creation of a bound state...

 per nucleon will reach a local maximum and thus that particular configuration will have a longer lifetime than nearby isotopes that do not possess filled shells.

A filled shell would have "magic numbers
Magic number (physics)
In nuclear physics, a magic number is a number of nucleons such that they are arranged into complete shells within the atomic nucleus...

" of neutrons and protons. One possible magic number of neutrons for spherical nuclei is 184, and some possible matching proton numbers are 114, 120 and 126 – which would mean that the most stable spherical isotopes would be ununquadium
Ununquadium
Ununquadium is the temporary name of a radioactive chemical element with the temporary symbol Uuq and atomic number 114. There is no proposed name yet, although flerovium has been discussed in the media.About 80 decays of atoms of...

-298, unbinilium
Unbinilium
Unbinilium , also called eka-radium or element 120, is the temporary, systematic element name of a hypothetical chemical element in the periodic table that has the temporary symbol Ubn and has the atomic number 120....

-304 and unbihexium
Unbihexium
Unbihexium , also known as eka-plutonium or element 126, is a hypothetical chemical element with atomic number 126 and symbol Ubh. It is of interest because of its location at the peak of the hypothesized island of stability.-History:...

-310. Of particular note is Ubh-310, which would be "doubly magic" (both its proton number of 126 and neutron number
Neutron number
The neutron number, symbol N, is the number of neutrons in a nuclide.Atomic number plus neutron number equals mass number: Z+N=A....

 of 184 are thought to be magic) and thus the most likely to have a very long half-life. (The next lighter doubly magic spherical nucleus is lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

-208, the heaviest stable nucleus and most stable heavy metal.)

Recent research indicates that large nuclei are deformed, causing magic numbers to shift. Hassium
Hassium
Hassium is a synthetic element with the symbol Hs and atomic number 108. It is the heaviest member of the group 8 elements. The element was first observed in 1984...

-270 is now believed to be a doubly magic deformed nucleus, with deformed magic numbers 108 and 162. However, it has a half-life of only 3.6 seconds.

Isotopes have been produced with enough protons to plant them upon an island of stability but with too few neutrons to even place them upon the island's outer "shores". It is possible that these elements possess unusual chemical properties and, if they have isotopes with adequate lifespans, would be available for various practical applications (such as particle accelerator targets and as neutron source
Neutron source
A Neutron source is a device that emits neutrons. There is a wide variety of different sources, ranging from hand-held radioactive sources to neutron research facilities operating research reactors and spallation sources...

s as well).

Half-lives of the highest-numbered elements


All elements with an atomic number above 82 (lead) are unstable, and the "stability" (half-life of the longest-lived known isotope) of elements generally decreases with rising atomic numbers from the relatively stable uranium (92) upwards to the heaviest known element: 118. It increases very slightly in the range of elements 110 to 113, hypothesized to be at the beginning of the island of stability. The longest-lived observed isotopes of each of the heaviest elements are shown in the following table.
Known isotopes of elements 100 through 118
Number Name Longest-lived
isotope
Half-life Article
100 Fermium
Fermium
Fermium is a synthetic element with the symbol Fm. It is the 100th element in the periodic table and a member of the actinide series. It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities,...

 
257Fm Isotopes of fermium
Isotopes of fermium
Fermium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered was 255Fm in 1952. 250Fm was independently synthesized shortly after the discovery of 255Fm...

101 Mendelevium
Mendelevium
Mendelevium is a synthetic element with the symbol Md and the atomic number 101. A metallic radioactive transuranic element in the actinide series, mendelevium is usually synthesized by bombarding einsteinium with alpha particles. It was named after Dmitri Ivanovich Mendeleev, who created the...

 
258Md Isotopes of mendelevium
Isotopes of mendelevium
Mendelevium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 256Md in 1955. There are 18 known radioisotopes, ranging in atomic mass from 245Md to 262Md, and 5 isomers...

102 Nobelium
Nobelium
Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union...

 
259No Isotopes of nobelium
Isotopes of nobelium
Nobelium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 254No in 1966. There are 16 known radioisotopes which are 248No and 250No to 264No, and 3 isomers, 251mNo, 253mNo,...

103 Lawrencium
Lawrencium
Lawrencium is a radioactive synthetic chemical element with the symbol Lr and atomic number 103. In the periodic table of the elements, it is a period 7 d-block element and the last element of actinide series...

 
262Lr Isotopes of lawrencium
Isotopes of lawrencium
Lawrencium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 258Lr in 1961. There are eleven known radioisotopes from 252Lr to 262Lr, and 1 isomer . The longest-lived isotope...

104 Rutherfordium
Rutherfordium
Rutherfordium is a chemical element with symbol Rf and atomic number 104, named in honor of New Zealand physicist Ernest Rutherford. It is a synthetic element and radioactive; the most stable known isotope, 267Rf, has a half-life of approximately 1.3 hours.In the periodic table of the elements,...

 
267Rf Isotopes of rutherfordium
Isotopes of rutherfordium
Rutherfordium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was either 259Rf in 1966 or 257Rf in 1969. There are 15 known radioisotopes from 253Rf to 268Rf and 4 isomers...

105 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...

 
268Db Isotopes of dubnium
Isotopes of dubnium
Dubnium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 261Db in 1968. There are 12 known radioisotopes from 256Db to 270Db, and 1-3 isomers...

106 Seaborgium
Seaborgium
Seaborgium is a synthetic chemical element with the symbol Sg and atomic number 106.Seaborgium is a synthetic element whose most stable isotope 271Sg has a half-life of 1.9 minutes. A new isotope 269Sg has a potentially slightly longer half-life based on the observation of a single decay...

 
271Sg Isotopes of seaborgium
Isotopes of seaborgium
Seaborgium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 263mSg in 1974. There are 12 known radioisotopes from 258Sg to 271Sg and 2 known isomers...

107 Bohrium
Bohrium
Bohrium is a chemical element with the symbol Bh and atomic number 107 and is the heaviest member of group 7 .It is a synthetic element whose most stable known isotope, 270Bh, has a half-life of 61 seconds...

 
270Bh Isotopes of bohrium
Isotopes of bohrium
Bohrium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 262Bh in 1981. There are 12 known isotopes ranging from 260Bh to 275Bh, and 1 isomer, 262mBh...

108 Hassium
Hassium
Hassium is a synthetic element with the symbol Hs and atomic number 108. It is the heaviest member of the group 8 elements. The element was first observed in 1984...

 
277Hs Isotopes of hassium
Isotopes of hassium
Hassium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 265Hs in 1984. There are 12 known isotopes from 263Hs to 277Hs and 1-4 isomers...

109 Meitnerium
Meitnerium
Meitnerium is a chemical element with the symbol Mt and atomic number 109. It is placed as the heaviest member of group 9 in the periodic table but a sufficiently stable isotope is not known at this time which would allow chemical experiments to confirm its position, unlike its lighter...

 
278Mt Isotopes of meitnerium
Isotopes of meitnerium
Meitnerium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 266Mt in 1982 . There are seven known isotopes, from 266Mt to 278Mt...

110 Darmstadtium
Darmstadtium
Darmstadtium is a chemical element with the symbol Ds and atomic number 110. It is placed as the heaviest member of group 10, but no known isotope is sufficiently stable to allow chemical experiments to confirm its placing in that group...

 
281Ds Isotopes of darmstadtium
Isotopes of darmstadtium
Darmstadtium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 269Ds in 1994. There are 7 or 8 known radioisotopes from 267Ds to 281Ds and 2 or 3 known isomers...

111 Roentgenium
Roentgenium
Roentgenium is a synthetic radioactive chemical element with the symbol Rg and atomic number 111. It is placed as the heaviest member of the group 11 elements, although a sufficiently stable isotope has not yet been produced in a sufficient amount that would confirm this position as a heavier...

 
281Rg Isotopes of roentgenium
Isotopes of roentgenium
Roentgenium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 272Rg in 1994, which is also the only directly synthesized isotope, all others are decay products of ununtrium,...

112 Copernicium  285Cn Isotopes of copernicium
113 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...

 
286Uut Isotopes of ununtrium
Isotopes of ununtrium
Ununtrium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 284Uut as a decay product of 288Uup in 2003. The first isotope to be directly synthesized was 278Uut in 2004. There...

114 Ununquadium
Ununquadium
Ununquadium is the temporary name of a radioactive chemical element with the temporary symbol Uuq and atomic number 114. There is no proposed name yet, although flerovium has been discussed in the media.About 80 decays of atoms of...

 
289Uuq Isotopes of ununquadium
Isotopes of ununquadium
Ununquadium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 289Uuq in 1999 . Ununquadium has five confirmed isotopes, and possibly 2 nuclear isomers...

115 Ununpentium
Ununpentium
Ununpentium is the temporary name of a synthetic superheavy element in the periodic table that has the temporary symbol Uup and has the atomic number 115....

 
289Uup Isotopes of ununpentium
Isotopes of ununpentium
Ununpentium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 288Uup in 2004. There are four known radioisotopes from 287Uup to 290Uup...

116 Ununhexium
Ununhexium
Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. There is no proposed name yet although moscovium has been discussed in the media.It is placed as the heaviest member of group 16 although a sufficiently stable isotope is...

 
293Uuh Isotopes of ununhexium
Isotopes of ununhexium
Ununhexium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 293Uuh in 2000. There are four known radioisotopes from 290Uuh to 293Uuh...

117 Ununseptium
Ununseptium
Ununseptium is the temporary name of a superheavy artificial chemical element with temporary symbol Uus and atomic number 117. Six atoms were detected by a joint Russia–US collaboration at Dubna, Moscow Oblast, Russia, in 2009–10...

 
294Uus Isotopes of ununseptium
Isotopes of ununseptium
Ununseptium is the most-recently synthesized artificial element, and much of the data is hypothetical. As any artificial element, a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotopes to be synthesized were 293Uus and 294Uus in 2009...

118 Ununoctium
Ununoctium
Ununoctium is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo. It is also known as eka-radon or element 118, and on the periodic table of the elements it is a p-block element and the last one of the 7th period. Ununoctium is...

 
294Uuo Isotopes of ununoctium
Isotopes of ununoctium
Ununoctium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 294Uuo in 2006. All data is hypothetical...

(Note that for elements 109-118 the longest-lived known isotope is always the heaviest one discovered, making it likely that there are still longer-lived isotopes among the undiscovered heavier ones)

For comparison, the shortest-lived element with atomic number below 100 is francium
Francium
Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K.Actually the least unstable isotope, francium-223 It has the lowest electronegativity of all known elements, and is the second rarest naturally occurring element...

 (element 87) with a half-life of 22 minutes.

The half-lives
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 nuclei in the island of stability itself are unknown since none of the isotopes that would be "on the island" have been observed. Many physicists think they are relatively short, on the order of minutes or days. Some theoretical calculations indicate that their half-lives may be long, on the order of 109 years.

The alpha-decay half-lives of 1700 nuclei with 100 ≤ Z ≤ 130 have been calculated in a quantum tunneling model with both experimental and theoretical alpha-decay Q-values. The theoretical calculations are in good agreement with the available experimental data.


Island of relative stability


(thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....

), and (uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

) are the only naturally occurring isotopes beyond bismuth
Bismuth
Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...

 that are relatively stable over the current lifespan of the universe. Bismuth was found to be unstable in 2003, with an α
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...

-emission half-life of years for . All other isotopes beyond bismuth are relatively or very unstable. So the main periodic table ends at bismuth, with an island at thorium and uranium. Between bismuth and thorium there is a "sea of instability", which renders such elements as astatine
Astatine
Astatine is a radioactive chemical element with the symbol At and atomic number 85. It occurs on the Earth only as the result of decay of heavier elements, and decays away rapidly, so much less is known about this element than its upper neighbors in the periodic table...

, radon
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...

, and francium
Francium
Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K.Actually the least unstable isotope, francium-223 It has the lowest electronegativity of all known elements, and is the second rarest naturally occurring element...

 extremely short-lived relative to all but the heaviest elements found so far.

Current theoretical investigation indicates that in the region and , a small "island"/"peninsula" might be stable with respect to fission and beta decay, such superheavy nuclei undergoing only alpha decay. Also, is not the center of the magic island as predicted earlier. On the contrary, the nucleus with , appears to be near the center of a possible "magic island" . In the region the beta-stable, fission survived is predicted to have alpha-decay half-life ~3.2 hours that is greater than that (~28 s) of the deformed doubly magic . The superheavy nucleus has not been produced in the laboratory as yet (2009). For superheavy nuclei with and the alpha-decay half-lives are predicted to be less than one second. The nuclei with , 124, 126 and are predicted to form spherical doubly magic nuclei and be stable with respect to fission. Calculations in a quantum tunneling model show that such superheavy nuclei would undergo alpha decay within microseconds or less.

Synthesis problems


The manufacture of nuclei on the island of stability proves to be very difficult because the nuclei available as starting materials do not deliver the necessary sum of neutrons. For the synthesis of isotope 298 of element 114
Ununquadium
Ununquadium is the temporary name of a radioactive chemical element with the temporary symbol Uuq and atomic number 114. There is no proposed name yet, although flerovium has been discussed in the media.About 80 decays of atoms of...

, one could use an isotope of plutonium and one of calcium that together have a sum of at least 298 nucleons; for example, calcium-50 and plutonium-248. However, these and heavier isotopes are not available in measurable quantities, making production virtually impossible with current methods. The same problem exists for the other possible combinations of isotopes needed to generate elements on the island using target-projectile methods. It may be possible to generate the isotope 298 of element 114, if the multi-nucleon transfer reactions would work in low-energy collisions of actinide nuclei.
One of these reactions may be:
248Cm + 238U → 298Uuq + 186W + 2

See also

  • Ununquadium
    Ununquadium
    Ununquadium is the temporary name of a radioactive chemical element with the temporary symbol Uuq and atomic number 114. There is no proposed name yet, although flerovium has been discussed in the media.About 80 decays of atoms of...

     — Unbinilium
    Unbinilium
    Unbinilium , also called eka-radium or element 120, is the temporary, systematic element name of a hypothetical chemical element in the periodic table that has the temporary symbol Ubn and has the atomic number 120....

     — Unbihexium
    Unbihexium
    Unbihexium , also known as eka-plutonium or element 126, is a hypothetical chemical element with atomic number 126 and symbol Ubh. It is of interest because of its location at the peak of the hypothesized island of stability.-History:...

  • Table of nuclides
  • Periodic table
    Periodic table
    The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...

     and Periodic table (extended)
  • Island of inversion
    Island of inversion
    An island of inversion is a region of the chart of nuclides that contains isotopes with a non-standard ordering of single particle levels in the nuclear shell model. Such an area was first described in 1975 by French physicists carrying out spectroscopic mass measurements of exotic isotopes of...


External links