Island of stability

The chemical elements beyond lead are radioactive, and they do not have stable isotopes. This means that they will decay into other elements. As their atomic number (the number of protons in their nucleus) increases, the time it takes for them to decay tends to get shorter, going from billions of years to less than one millisecond. There is a theory in physics that says that after a number of elements with short half lives, there will be others with longer half lives. These are generally known as "islands of stability". These elements are expected to have isotopes that decay in several minutes.The theory is that, similarly to electron shells, the nucleus of an atom is made of "shells" (which can be thought of as layers of protons and neutrons), and that when a nucleus has entirely filled shells, it is significantly more stable.

A filled shell would have "magic numbers" of neutrons and protons, known magic numbers are 2, 8, 20, 28, 50, 82, and 126; however, further numbers are predicted to exist. One element that is predicted to be quite stable is unbihexium, in particular, its isotope unbihexium-310, which would be "doubly magic" (both its atomic number of 126 and neutron number of 184 are thought to be magic) and so would be the most likely to be very stable. The next lightest doubly magic isotope of an element is lead-208, the heaviest stable isotope of any element and the most stable heavy metal.

Isotopes have been produced with enough protons to put them on an island of stability but with too few neutrons. It is possible that these elements possess unusual properties and, if they have isotopes with long enough lifespans, would be available for various uses (such as particle accelerator targets and neutron sources).

Periodic table with elements colored according to the half-life of their most stable isotope.      Stable elements.      Radioactive elements with half-lives of over four million years.      Half-lives between 800 and 34,000 years.      Half-lives between 1 day and 103 years.      Half-lives ranging between a minute and 1 day.      Half-lives less than a minute.

Island Of Stability Media

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  A diagram by the Joint Institute for Nuclear Research showing the measured (boxed) and predicted half-lives of superheavy nuclides, ordered by number of protons and neutrons. The expected location of the island of stability around Z = 112 is circled.

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  Chart of half-lives of known nuclides

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  Diagram showing energy levels of known and predicted proton shells (left and right show two different models). The gaps at Z = 82, 114, 120, and 126 correspond to shell closures, which have particularly stable configurations and thus result in more stable nuclei.

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  A summary of observed decay chains in even-Z superheavy elements, including tentative assignments in chains 3, 5, and 8. There is a general trend of increasing stability for isotopes with a greater neutron excess (N − Z, the difference in the number of protons and neutrons), especially in elements 110, 112, and 114, which strongly suggests that the center of the island of stability lies among even heavier isotopes.

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  A diagram depicting predicted decay modes of superheavy nuclei, with observed nuclei given black outlines. The most neutron-deficient nuclei as well as those immediately beyond the shell closure at N = 184 are predicted to predominantly undergo spontaneous fission (SF), whereas alpha decay (α) may dominate in neutron-deficient nuclei closer to the island, and significant beta decay (β) or electron capture (EC) branches may appear closest to the center of the island around 291Cn and 293Cn.

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  This chart of predicted decay modes, derived from theoretical research of the Japan Atomic Energy Agency, predicts the center of the island of stability around 294Ds; it would be the longest-lived of several relatively long-lived nuclides primarily undergoing alpha decay (circled). This is the region where the beta-stability line crosses the region stabilized by the shell closure at N = 184.

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  Three-dimensional rendering of the island of stability around N = 178 and Z = 112

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  This chart of nuclides used by the Japan Atomic Energy Agency shows known (boxed) and predicted decay modes of nuclei up to Z = 149 and N = 256. Regions of increased stability are visible around the predicted shell closures at N = 184 (294Ds–298Fl) and N = 228 (354126), separated by a gap of short-lived fissioning nuclei (t1/2