Where do the heaviest elements come from?

[aaricia]

Hello there!

First of all, I couldn't find this topic around here but I could be blind, so if the answer is posted somewhere else, just leave me the link as a response, thank you!

I am trying to figure out few things about where the heaviest elements come from. I know that Iron is the heaviest one created in a star, and then with the supernovas we get until uranium and plutonium (not quiet sure which one, I would like to know if plutonium is a result of uranium decay or is created in a supernova as well ).

In the periodic table, after plutonium, you can find few other actinoids: Are they created artificially or did they exist in nature but they decayed here in Earth long time ago and we can't find them nowadays? Or do we actually find them somewhere in nature? And about the rest of elements after the last of the actinoids, are they artificial? and why are they classified as "unknown chemical properties"?

I was discussing with a friend some time ago about creating a new element that doesn't exist naturally; he thought it was impossible, but as far as I know it is possible. Or am I wrong? I heard somewhere that some elements' life are so short because they are very unstable. Are these the ones in the category "unknown chemical properties"? Is that why we can't find them in nature or they just created in a lab?

Thanks a lot for any answers, and excuse my poor knowledge about this subject, really!

 

[mathman]

Elements past Uranium may have been created in supernovae, but their half lives are so short (even Plutonium) that they all decayed. All those that are described are "artificial", that is made in physics labs, etc.

http://en.wikipedia.org/wiki/Transuranium_element

 

[Chronos]

Californium, atomic number 98, is the heaviest element believed to be naturally created [in supernova explosions]. Elements up to atomic number 118 [ununoctium] have been created in the laboratory. Virtually all elements heavier than bismuth are radioactive and most have very brief half lives. The putative element number 118 has a half life of about 14 milliseconds. These brief half lives make learning their chemical properties - challenging.

 

[mfb]

and why are they classified as "unknown chemical properties"?

If you can just synthesize a few atoms within some weeks (and those decay in microseconds to minutes), you cannot study things like a melting point of the material. Some chemical reactions can be studied within seconds, but even that is tricky.

 

[aaricia]

thanks so much for the fast answers
do we use these heavy short-life elements for something practical, like the fermium (100) or the bohrium (107)?

 

[twofish-quant]

Californium, atomic number 98, is the heaviest element believed to be naturally created [in supernova explosions].

I think this isn't the case. Supernova will produce anything and everything. It's just that most of those elements will decay pretty quickly.

Californium is interesting because at one point people thought that they detected it in supernova, but it turns out that they didn't

 

[mfb]

do we use these heavy short-life elements for something practical, like the fermium (100) or the bohrium (107)?

Americium (Z=95) and Curium (Z=96) are used as source of alpha radiation, with Am in smoke detectors as a widespread application.
Californium (Z=98) seems to have some special applications.
Mendelevium (Z=101) is the last element with reasonable lifetime, but I don't think it has some useful application. All heavier elements decay within hours or a few days, so you cannot store them.

 

[aaricia]

I see, thanks again!