[Kryptid]

Neutron stars are made of only neutrons. In order for something to be considered an atom, it must contain protons and electrons. Neutron stars have neither.

By the way, bismuth was recently discovered to have no stable isotopes. It is always radioactive, but it has an extremely long half-life. That makes lead the heaviest non-radioactive element.

I think plutonium also occurs naturally, but in only very trace amounts.

[Ylide]

Bismuth is radioactive?  What is it's mechanism of decay?  Where did you hear this?

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[qpan]

Supercryptid- you do appear to be right!
http://www.cnrs.fr/cw/en/pres/compress/bismuth.htm



"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe

[gsmollin]

If GUTs are right, and the proton IS unstable (1/2 life >10e30 y), then all the elements are radioactive.

[qpan]

quote:Originally posted by gsmollin

If GUTs are right, and the proton IS unstable (1/2 life >10e30 y), then all the elements are radioactive.

True- the proton has a half life estimated to be greater than 1x10^32 years, but no-one has ever observed such a decay!

"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe

[Ylide]

Qualitatively speaking, I think I'd call something with a half-life in an order of magnitude of 10^19 years pretty stable.  It's numerically closer to the radioactive stability of a proton than it is to that of radioactive nuclei with a half life of less than approx. 2000 years. (i.e. most of them)

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[Titanscape]

This is all interesting, I had never heard of thses facts about neutron stars before. What about quasars and brown dwarfs? Could circumstances exist within them leading to unusualy large stable elements? Or even deep inside the earth, stable for years wheras in a vacuum only seconds?

Titanscape

[mirormimic]

quote author=tweener link=topic=1013.msg8752#msg8752 date=1086149020]
In terms of atomic number, what element is the largest naturally occurring atom?  I know there are several man-made elements that are larger but unstable.  Why are they unstable?  Why is there an upper limit on the size (in nature anyway)?

----
John - The Eternal Pessimist.
[/quote]

Atoms are of a consistent size and and enclose a consistent "volume" of space energy. The only  definitive thing that has been concluded as to atom size is that it is very minuscule. However the "size" of the light energy rays emitted from an atom grow as the light from the atom is communicated through space. If these light energy rays come into relativity to a reflective plane( aether, brane)the illusion of atomic expansion occurs. That is to say if the energy light from an atom has traveled away from the atom 1 light year and its light rays is communicated to a reflective platform( stratum, reflective medium relative to light)the reflected "image" light FORM of  the atom is such and such diameter. If that same atomic energy-light ray travels 100 light years before "colliding" with a reflective plane( membrane)then its reflected light FORM "image" diameter will be significantly larger. As an extention: If the atom is reflected at a point in space that is 1 mile (5,280 ft.)away from atom then the size(diameter) of ITS "reflected image" would almost epitomize the size of the atom itself.

Thus: Atoms are of a definitive size and represent a profound amount of energy and light being compacted into a small" package". When we perceive "mass object(s)" we are actually viewing magnified ( reflected) atom or group of atoms. Thus the size of the "material" object( Lead; for instance) is NOT The actual size of the atoms...rather represent a  smaller component part of ( atom) or a group of component parts( conglomeration of atoms)producing Lead.

Thus: The size and diameter of any "mass" object ( large verses smaller) indicates how far that REFLECTED object is from its reflector atom( or group of atoms). Postulate: The larger a "mass object"(B) is the farther it is away from the "atom/atoms"(A) that is being reflected to "mass object"(B). Further: The smaller the diameter of "mass object" the closer it is to the "atom/atoms" that is being reflected to "mass object".

Note: The smaller the perceived "mass"(B) the closer the potentiality for conversion to energy(A). The larger the diameter of  reflected "mass object"(B) the lesser the potentiality of conversion.

A=B.......Where A is atom( light-energy); where B is reflected of A. The distance between the reflector(A) and its reflected image(B) dictates the potentiality ( or not) of conversion. conversion= A ceasing to reflect at B(point in space) resulting in B( mass object) converting back to the singular whole of A. ( B conversion to A represents the "relative duality " of B as to A changing back to A singular.....non-dualized; non-reflected)

[syhprum]

The questioner asks what is the largest atom and all the replies have discussed the most massive, are there not some bloated atoms that are larger than the more massive ?

[nwilliams]

Researchers are attempting the new and the most largest atoms to formed by smashing with the other atoms. They would keep trying to creates the most largest atoms. But the heavenly atom found in the Uranium 92. Whenever, there is the a new creation of the atoms they are not see easily due to some scientific reasons.

[yor_on]

Originally posted by gsmollin</i>

If GUTs are right, and the proton IS unstable (1/2 life >10e30 y), then all the elements are radioactive.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

True- the proton has a half life estimated to be greater than 1x10^32 years, but no-one has ever observed such a decay!

"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe

I have an unlimited patience.
Will that help?
==

sort of missed the second page here

[Soul Surfer]

If you include the size of the electron cloud round the neutral atom the largest atoms are those with the most loosely bound electrons notably the alkali metals.  The largest stable alkali metal is Caesium.  Francium would be larger but is radioactive and therefore not stable