[dorratz]

Hello

I have a question: what is the most heavy natural element?

[Borek]

What do you mean by 'heavy'? The most dense? Google "the most dense element" and you will have answer on your screen. Heavy in terms of nucleus size? Check our periodic table (menu on the left).

[Albert]

I think it's a matter of atomic mass, isn't it? Well, I'd say Uranium.

[dorratz]

Yhh, I meant the atomic mass - so this is Uranium - well thank you!

[Mitch]

Plutonium is the heaviest you can find naturally made on Earth.

http://www.nsf.gov/od/nms/recip_details.cfm?recip_id=172

[Will]

I would probably agree with what Mitch said but http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0009901.html says that Americium occurs in nature, but most websites say it can't be found in nature .

There were a few websites that said Curium probably could be found in nature but it hasn't been found yet.

This website: http://www.staff.uni-marburg.de/~kernchem/kern07-e.htm(and loads others) says that Pu is the heaviest naturally occuring element.

I don't know what to think !

[Mitch]

Americium and Curium can be found in nature, now, due to nuclear bomb testing. But the heaviest naturally occuring element is Plutonium.

[Will]

ooooooooo that would make sense. thanks

[wereworm73]

It's possible for americium-240 to exist naturally, though it would have to happen like this...

Pu-244 (from supernovae debris) ---> U-240 ---> Np-240 ----> Pu-240 ----> Am-240

OR

U-238 (from uranium ore) ---> U-239 (absorbing a neutron from a spontaneous fission reaction of a neighboring uranium atom) ---> Np-239 ---> Pu-239 ---> Pu-240 (neutron from spontaneous fission of a neighboring atom) ---> Am-240