How Many Elements

[iansterling]

How many elements have been discovered? Only 118 on the periodic table. i thought there were 128 with 2 more spare for assumed elements known but not found.

[ABerrant]

https://en.wikipedia.org/wiki/Extended_periodic_table

[ToraToraTora]

traditional there are 92 occuring in nature, the rest are created by man made processes like fusion or momentarily in atom smashers like the LHC

[jim360]

I'm no expert, but the LHC has nothing to do with creating new elements, focusing as it does on what goes on at a smaller scale. On occasion ALICE (one of the four main experiments) smashes lead nuclei together, but even then the resulting mess is made up not of elements old or new, but of what's known as a "quark-gluon plasma". If you want to make new elements, experiments elsewhere, such as at Helmholtz and Dubna, focus on that. That said, the principles behind both are essentially the same. The main point about the LHC though is that it doesn't put the right stuff in to create a new element, and operates at too high energies.

[ToraToraTora]

fair enough jim but I was under the impression that some man mad processes create these elements that exist only for nano seconds due to their instability. I do not know the exact processes I was merely trying to say that they are not naturally occurring.

[jim360]

Yes, you're right about the rest of it -- most of the heavier elements have to be produced in a lab. I think some elements heavier than Uranium do occur, or can be produced, naturally in small amounts, mostly plutonium. I think the threshold for "possibly natural" to "almost certainly artificial" is at element number 100, fermium.

The important threshold numbers are:

43 -- Technetium, lightest element that is never stable.
82 -- Lead, heaviest element that has a stable form.
94 -- Plutonium, heaviest element that is still observed naturally.
100 -- fermium, heaviest element that existed naturally, but then it was only created in "freak" circumstances where enough uranium was concentrated in one place, to create a "natural nuclear reactor" (in Gabon).

Above fermium, every element decays so quickly that it's essentially useless apart from to scientists, with half-lives measured in hours or even fractions of a second.

[mushroom25]

here's a list dating from 1959, which included the 102 then known -


clearly more have been "discarvard" since then....