Editing Extended periodic table (section)

====Predicted decay properties of undiscovered elements====
As the main island of stability is thought to lie around <sup>291</sup>Cn and <sup>293</sup>Cn, undiscovered elements beyond [[oganesson]] may be very unstable and undergo [[alpha decay]] or [[spontaneous fission]] in microseconds or less. The exact region in which half-lives exceed one microsecond is unknown, though various models suggest that isotopes of elements heavier than [[unbinilium]] that may be produced in fusion reactions with available targets and projectiles will have half-lives under one microsecond and therefore may not be detected.<ref name=Karpov/> It is consistently predicted that there will exist regions of stability at ''N'' = 184 and ''N'' = 228, and possibly also at ''Z'' ~ 124 and ''N'' ~ 198. These nuclei may have half-lives of a few seconds and undergo predominantly alpha decay and spontaneous fission, though minor [[positron emission|beta-plus decay]] (or [[electron capture]]) branches may also exist.<ref name=Palenzuela>{{cite journal|last1=Palenzuela|first1=Y. M.|last2=Ruiz|first2=L. F.|last3=Karpov|first3=A.|last4=Greiner|first4=W.|year=2012|title=Systematic Study of Decay Properties of Heaviest Elements|journal=Bulletin of the Russian Academy of Sciences: Physics|volume=76|issue=11|pages=1165–1171|issn=1062-8738|url=http://nrv.jinr.ru/karpov/publications/Palenzuela12_BRAS.pdf|doi=10.3103/S1062873812110172|bibcode=2012BRASP..76.1165P|s2cid=120690838}}</ref> Outside these regions of enhanced stability, [[fission barrier]]s are expected to drop significantly due to loss of stabilization effects, resulting in fission half-lives below [[attosecond|10<sup>−18</sup>]] seconds, especially in [[even and odd atomic nuclei|even–even nuclei]] for which hindrance is even lower due to [[nucleon pair breaking in fission|nucleon pairing]].<ref name=SHlimit/> In general, alpha decay half-lives are expected to increase with neutron number, from nanoseconds in the most neutron-deficient isotopes to seconds closer to the [[beta-stability line]].<ref name="sciencedirect1"/> For nuclei with only a few neutrons more than a magic number, [[nuclear binding energy|binding energy]] substantially drops, resulting in a break in the trend and shorter half-lives.<ref name="sciencedirect1"/> The most neutron deficient isotopes of these elements may also be unbound and undergo [[proton emission]]. [[Cluster decay]] (heavy particle emission) has also been proposed as an alternative decay mode for some isotopes,<ref>{{cite journal |last1=Poenaru |first1=Dorin N. |last2=Gherghescu |first2=R. A. |last3=Greiner |first3=W. |date=2012 |title=Cluster decay of superheavy nuclei |url=https://www.researchgate.net/publication/235507943 |journal=Physical Review C |volume=85 |issue=3 |pages=034615 |doi=10.1103/PhysRevC.85.034615 |access-date=2 May 2017|bibcode=2012PhRvC..85c4615P }}</ref> posing yet another hurdle to identification of these elements.