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The island of stability is a term from nuclear physics that describes the possibility of elements with particularly stable "magic numbers" of protons and neutrons. This would allow certain isotopes of some transuranic elements to be far more stable than others, that is, decay much more slowly.

Contents 1 Half-lives of large isotopes 2 Island of relative stability 3 Synthesis problems 4 References 5 See also 6 External links

The idea of the island of stability was first proposed by Glenn T. Seaborg. The hypothesis is that the atomic nucleus is built up in "shells" in a manner similar to the electron shells in atoms. In both cases shells are just groups of quantum energy levels that are relatively close to each other. Energy levels from quantum states in two different shells will be separated by a relatively large energy gap. So when the numbers of neutrons and protons completely fill the energy levels of a given shell in the nucleus, then the binding energy per nucleon will reach a local minimum and thus that particular configuration will have a longer lifetime than nearby isotopes that do not have filled shells^[1].

A filled shell would have "magic numbers" of neutrons and protons. One possible magic number of neutrons is 184, and some possible matching proton numbers are 114, 120 and 126 — which would mean that the most stable possible isotopes would be ununquadium-298, unbinilium-304 and unbihexium-310. Of particular note is Ubh-310, which would be "doubly magic" (both its proton number of 126 and neutron number of 184 are thought to be magic) and thus the most likely to have a very long half-life. (The next lighter doubly-magic nucleus is Lead-208, the heaviest stable nucleus and most stable heavy metal.) None of these transuranic isotopes has yet been produced, but isotopes of elements in the range between 110 through 114 are slower to decay than isotopes of nearby nuclei on the periodic table.

Fermium is the largest element that can be produced in a nuclear reactor. The stability (half-life of the longest-lived isotope) of elements generally decreases from element 101 to element 109 and then approaches an island of stability with longer-lived isotopes in the range of elements 111 and 114^[2]. This is illustrated in the following two tables.

Isotopes of elements 100 through 109^[2]

Number	Name	Longest-lived isotope	Half-life of longest-lived isotope	Link
100	fermium	257Fm	101 days	Isotopes of fermium
101	mendelevium	258Md	52 days	Isotopes of mendelevium
102	nobelium	259No	58 minutes	Isotopes of nobelium
103	lawrencium	262Lr	215 minutes	Isotopes of lawrencium
104	rutherfordium	261Rf	13 hours	Isotopes of rutherfordium
105	dubnium	262Db	32 hours	Isotopes of dubnium
106	seaborgium	266Sg	2.4 minutes	Isotopes of seaborgium
107	bohrium	267Bh	22 seconds	Isotopes of bohrium
108	hassium	270Hs	22 seconds	Isotopes of hassium
109	meitnerium	268Mt	720 milliseconds	Isotopes of meitnerium

The following table shows information about the half-lives of isotopes of elements 110 through 120.

Isotopes of elements 110 through 120

Number	Name	# isotopes (known)	# isotopes observed	Longest half-life observed (ms)	Link
110	darmstadtium	15	10	11,100	Isotopes of darmstadtium
111	roentgenium	12	4	3,600	Isotopes of roentgenium
112	ununbium	9	1	300,000	Isotopes of ununbium
113	ununtrium	6	2	480	Isotopes of ununtrium
114	ununquadium	5	4	2,800	Isotopes of ununquadium
115	ununpentium	5	2	87	Isotopes of ununpentium
116	ununhexium	5	4	61	Isotopes of ununhexium
117	ununseptium	2	0	N/A	Isotopes of ununseptium
118	ununoctium	1	1	0.89	Isotopes of ununoctium
119	ununennium	0	0	N/A	Isotopes of ununennium
120	unbinilium	0	0	N/A	Isotopes of unbinilium

The half lives of elements in the island are uncertain. Many physicists think they are relatively short, on the order of minutes, hours, or perhaps days. However, some theoretical calculations indicate that their half lives may be long (some calculations put it on the order of 10⁹ years)^[3]. It is possible that these elements could have unusual chemical properties, and, if long lived enough, various applications (such as targets in nuclear physics and neutron sources). However, the isotopes of several of these elements still have too few neutrons to be stable. The island of stability still hasn't been reached, since the island's shores have neutron richer nuclides than those produced.

²³²Th (thorium), ²³⁵U and ²³⁸U (uranium) are the only naturally occurring isotopes beyond bismuth that are relatively stable over the current lifespan of the universe. Bismuth was found to be hypothetically unstable in 2003, with an α-emission half-life of 1.9 × 10¹⁹ years for Bi-209. 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 trough of severe instability, which renders such elements as astatine, radon, and francium extremely short-lived relative to all but the heaviest elements found so far.

Another island

The relatively unstable elements reach up to ²⁵⁷Fm (fermium), after which they get very unstable due to spontaneous fission until somewhat more stable, spherical nuclei are obtained at the island of stability. The center of this hypothetical island occurs at an atomic number of 114 and a neutron number of 184.

Manufacturing nuclei in the island of stability may be very difficult, because the nuclei available would not deliver the necessary sum of nuclei. So for the synthesis of isotope 298 of element 114 by using plutonium and calcium, one would require an isotope of plutonium and one of calcium, which have together a sum of at least 298 nucleons (more is better, because at the nuclei reaction some neutrons are emitted). This would require for example in the case of synthesis of element 114 the usage of calcium-50 and plutonium-248. However these isotopes (and heavier calcium and plutonium isotopes) are not available in weighable quantities. This is also the fact for other target/projectile-combinations.

However it may be possible to generate the isotope 298 of element 114, if nuclear transfer reactions would work. One of these reactions may be:

²⁰⁴Hg + ¹³⁶Xe → ²⁹⁸Uuq + ⁴⁰Ca + 2n

1. ^ Shell Model of Nucleus. HyperPhysics. Department of Physics and Astronomy, Georgia State University. Retrieved on January 22, 2007.
2. ^ ^{a b} Emsley, John (2001). Nature's Building Blocks, (Hardcover, First Edition), Oxford University Press, (pages 143,144,458). ISBN 0198503407. 
3. ^ Moller Theoretical Nuclear Chart 1997

• Island of stability : Ununquadium – Unbinilium – Unbihexium
• Isotope table and Isotope table (divided) - the best visualization of the island of stability
• Periodic table and Periodic table (extended)

• The synthesis of spherical superheavy nuclei in 48Ca induced reactions
• Uut and Uup Add Their Atomic Mass to Periodic Table
• New elements discovered and the island of stability sighted
• First postcard from the island of nuclear stability
• Second postcard from the island of stability
• Superheavy Elements "Island of Stability"
• Superheavy elements
• Can superheavy elements (such as Z=116 or 118) be formed in a supernova? Can we observe them?
• NOVA - Island of Stability
• http://www.lbl.gov/Science-Articles/Archive/elements-116-118.html
• New York Times Editorial by Olivar Sacks regarding the Island of Stability theory