h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

i have a problem,i have herd there are such elements as 113 115 117 118 they are on some perodic table but not others and if they are on there. theres no real info. now if we think we know enough bout unknow elements to put them on perodic tables can u pls explaian i hope some chemist can clear this all up and explain why they put unknow elements on periodic tables.

You can't to chemistry with these elements because they are mindbogglingly unstable. So you have to ask the physicist.

I *think* that all that's known about these elements is their atomic mass and their decay rates. For determining all other properties 1) you don't have enough of them, and 2) they are too unstable.

Quite, I recently looked up the heaviest elements and it becomes increasingly unlikely that you can actually believe that they formed. The research group claiming to have made the world record heaviest element (No. 123ish) claimed to have made only 1 atom of it and that it decayed after only a few nanoseconds.

I suspect their evidence for that might not stand up to close scrutiny. Even the so called "magic mountain" of stability turned otu to be disappointing as half lives were millisecond rather than nanosecond. They were still not stable. There is no element with a stable isotope heavier than Bismuth (atomic number 83).

Recently they've found out that even Bismuth has no stable isotope. Well, one element less.

Really?

It must have a phenomenally long half life.
Tell me more

See http://physicsweb.org/article/news/7/4/16 for details.

Twenty billion billion years eh? So most of it is still left then?
About a billion time longer than the universe is old

I still wouldn't advise telling Greenpeace about this mind you

Very interesting.

"Even the so called "magic mountain" of stability turned otu to be disappointing as half lives were millisecond rather than nanosecond"

I assume you're reffering to the "magic" element 114. If you look here: http://www.webelements.com/webelements/elements/text/Uuq/key.html you should find that one of the isotopes Uuq has a half life of 30 seconds. Not milliseconds. And that wasn'y the stbaly predicted form, as the stable number of neutrons "magic number" involves the Uuq having several more neutrons. This could give it a much greater stability and, if a cheaper production method could be devised, this could be of some use. Certainly it would prvide a stepping stone to higher elements.

Hmm, that's a completely different site to where I got my stuff (I was writing from memory anyway as I recall).
30 seconds huh, so any that you have made will be effectively gone in 300 seconds. Massively greater stablity will be needed for anything useful to be made.

Even if it gets more stable is it ever going to be truly stable? I suspect not. Finding a cheaper method of production is also tremendously unlikely in my opinion - I guess you could collect it during the next supernova if you want to risk it

These things, I think will never prove useful elements material wise but can provide much useful experimental evidence of theory so they have plenty of value there.

Yes, experimental evidence of theory is a good thing. That's the use for the higher elements that I put in my chemistry coursework anyway, so it better be right. I dont really trust my coursework skills at 2 in the morning.

Ah, but it is the only time for it to be done!

Yes, especially when it has to be in the next morning!