Here are some good links on the subject.
General information about atomic stability:
http://www.abc.net.au/science/k2/moments/s161220.htm
Detailed info about synthesizing heavy elements from the US Department of Energy:
http://www.eurekalert.org/features/doe/2002-01/drnl-pat062402.php
Originally posted by phoenixthoth
yes that does make some sense. what about 115?
are these elements radioactive? do they have fusion/fission potential use in energy sources (and weapons)? you said it was unclear what their shelf life is so that makes me think they are radioactive...
cheers,
phoenix
phoenix, they are indeed highly radioactive; this is what causes them to decay, hence they are unstable. They are so unstable that there doesn't appear to be any practical use for them, as far as energy extraction or weapons go. For instance, the US DoE link posted above tells us that synthesized isotopes of 110 have had half-lives ranging from 100 microseconds to 1.1 milliseconds. 114 was synthesized in 1998 as zooby pointed out, and it lasted 30 seconds before it began to decay, so relative to its atomic neighbors, at least, it is very stable.
I only did a quick google search, but I didn't find any indications that 115 has been synthesized. The fact that 114 only lasted 30 seconds before it started to decay seems to raise questions about how stable 115 could really be, however. It could be that another isotope of 114 would last longer, but probably not all that much longer. So while 115 might be stable relative to 110, I have my doubts that it would be stable enough to serve any long term use. Here's more cause for suspicion, again from the US DoE:
The proton shells of helium, oxygen, calcium, nickel, tin, and lead are completely filled and arranged such that the nucleus has achieved extra stability. The atomic numbers of these elements—2, 8, 20, 28, 50, and 82—are known as "magic numbers." These same numbers plus 126 are magic numbers for neutrons. Notice that the magic numbers are all even. No truly stable element heavier than nitrogen has an odd number of both protons and neutrons. Elements with even numbers of protons and neutrons make up about 90 percent of Earth's crust.
So if anything, it seems 115 would be less stable than 114 and 116, and wouldn't last long enough to serve any useful purpose.
For what it's worth, I also hunted up a page that claims to explain the utility of 115 for manipulating gravitational fields, and also lists its supposed chemical properties:
http://www.abovetopsecret.com/pages/element115.html