Re: Total number of elements in the universe?

I think I may have seen that documentary as well, and I admit it is slightly 
misleading. Uranium is an extremely dense metal (density isn't quite the same 
as mass, something can be quite heavy but not very dense), and is also the 
heaviest naturally occurring metal. If you have a copy of the periodic table 
(look at www.webelements.com if you don't), so can see that there are plenty 
of things with higher atomic numbers than 92 (Uranium's number).

However, these heavier atoms are unstable on Earth. They are simply "too 
heavy" to exist, and so decompose into smaller elements, which is the origin 
of radiation. Even some isotopes (variants) of uranium are radioactive, and 
they break down into Uranium 235 (a particular isotope that is stable). 
Perhaps at the centre of stars they might be stable, but even that is not 
100% known.

So Uranium isn't the heaviest possible element, but it is the heaviest stable 
element. I hope that answers your question.