Sciencemadness Discussion Board

The Periodic Table

Swede - 24-11-2012 at 17:22

Wikipedia has a decent article on the Periodic Table, including proposed variations.

Like so many chemists and hobbyists, finally understanding what the periodic table truly meant was groundbreaking intellectually, especially as it regards to electrons and how the element behaves chemically. It was like a light bulb was turned on. I think we can all thank Mendeleev for this beautiful tool!

I was reading up a bit on the Actinides, and the syntheses of everything above Uranium. And it is truly fascinating. There is a supposed "island of stability" between elements of ~110 to 114, whereby half-lives are measured in several seconds vs. micro or milliseconds.

I remember reading somehere that scientists had proposed that once we reach a certain number of protons, not only will there be an island of stability, there will be some nicely stable (but still radioactive) elements with half-lives measured perhaps in months or years.

Further, they claimed some pretty spectacular characteristics of these "super-heavy, super-stable" elements, stuff dealing with "extraterrestrials" and other junk science that sounded pretty far-fetched.

Has anyone else heard of this, or am I remembering it incorrectly?





[Edited on 25-11-2012 by Swede]

chemrox - 24-11-2012 at 18:41

I remember when the Russians claimed to have made the element they named Nobelium and our chemists churlishly referred to it as "no-believe-ium." And that just because we couldn't make it with our bevatron. I grew up in the same neighborhood as the nuclear physicist EO Lawrence and his daughter, Barbara, was a classmate. I never heard the "extraterrestrial" bit. Why would they be "extraterrestrial?" A supernova of sufficient magnitude to make these would explode with enough violence to send them through the galaxy wouldn't it? here's another thought; maybe these are so heavy that once they've taken the subduction escalator down they can't escape the gravity pull of the core. Unlike gold, they never come back up...and being relatively stable they sit there contributing to geothermal heat. Has anyone ever seen evidence of them as in a spectrograph from anywhere in space??

[Edited on 25-11-2012 by chemrox]

Swede - 25-11-2012 at 07:20

There has never been spectrographic evidence of super-heavy elements from space, but such evidence could easily be overwhelmed due to the tiny parts per quintiliion they would be, vs the massive amounts of elements 1 through 92, and especially everything below 26, Fe.

I'm not promoting some weird extraterrestrial agenda, just wondering if anyone smarter than me on these (which is 95% of those here, probably) have heard of this supposed theoretical Island of super-stability way up there on the periodic table. The ET stuff comes from claims from some nuts that ET's make use of these, and they are in fact stable.

blogfast25 - 25-11-2012 at 08:16

Recently (about 2 years ago) an Israeli scientist announced discovery of a stable super heavy, found in natural uranium, or so it was claimed. But it was never corroborated and must now be considered discarded science.

Eddygp - 25-11-2012 at 09:24

Would it be possible to have a single atom to be as large as a pea, wit a half life of some days, then? Wow, one single atom the size of a pea... or a car!

12AX7 - 25-11-2012 at 13:20

I think something with a few days' half life would be too hot to solidify any larger than a grain of dust, the internal heating would vaporize it! Very small particles could be created though, as well some basic compounds crystallized, chloride, oxide, etc.

The main drawback is how many billions of joules it takes to create a single atom (the reaction cross-section is minuscule), one which is hopelessly neutron-deficient. Making any macroscopic amount will take a tremendous amount of energy by any means.

Tim

phlogiston - 25-11-2012 at 15:37

The island of stability probably exists, but it is very difficult at present to synthesize even a few atoms of these elements and it is especially difficult to produce the isotopes that have enough neutrons to be stable. The atoms produced so far always are neutron-poor and have very short half-lifes.

A guy called Amnon Marinov claimed he recovered a tiny amount of a stable isotope of roentgenium (111) from gold, but his claim is extremely controversial.

The ET stuff I think is mostly based on a story told by Bob Lazar, incidentally also the guy who runs United Nuclear. He claimed to have worked in area 51 reverse engineering alien spacecraft and claimed they are propelled by a 'gravity amplifier' that requires element 115 which is supposedly present in mineable amounts on some other planets but not found in our solar system. The US government aledgedly bought a few tons of the stuff from the aliens. Entertaining reading.

watson.fawkes - 26-11-2012 at 05:33

Quote: Originally posted by Swede  
I remember reading somehere that scientists had proposed that once we reach a certain number of protons, not only will there be an island of stability, there will be some nicely stable (but still radioactive) elements with half-lives measured perhaps in months or years.
See also Wikipedia on magic numbers. Hassium has Z=108, the largest observed magic proton number. The double-magic isotope 270Hs has a lifetime of 22 s; see this story from 2006. (The Wikipedia page for Hs states a shorter half-life, but relies on a citation from 2001.) 108 is consider magic, but possibly not as magic as 126. We have a few years before we see Z=126 atoms being made. Its chemistry will be rather unique, though, as it will have ground state g electrons.