If the natural element of uranium decays to lead, what other elements naturally decay into others? For instance, could gold be the natural decayed remains of another element?
IIRC, I think every element with an atomic number of 86 (radon) or higher is naturally radioactive and will decay into “smaller” elements.
IIRC, helium is a common end-product of radioactive decay (i.e., beta particle decay).
Given enough time (read: continuously expanding universe leading to heat-death, and trillions of years after that), everything heavier than iron will eventually decay into iron (the most stable heavy element), and everything lighter will, I believe, either stay as-is, or decay into hydrogen. Not sure on the last part.
To answer the OP, though, it’s unlikely that gold (Z = 79) is the end product of recent nuclear decay. It would have to have come from a beta decay of radioactive platinum (which, if it exists, would only be man-made), or alpha decay of radioactive thallium (ditto). The only likely end products in any normal span of time are lead, bismuth possibly thallium (though likely only for manmade isotopes), and other radioactive elements.
(Note: I’m not including spontaneous fissions. These usually occur only with extremely heavy, manmade elements.)
For the record, no element with an atomic weight higher than Z = 83 is stable. Also, technetium (Z = 43) and promethium (Z = 61) have no stable isotopes. However, thorium, uranium, and plutonium (Z = 90, 92, 94) are somewhat stable in certain isotopes (with half-lives ranging into the billions of years) but they’re still highly radioactive. The end product of all of them is lead.
As an aside, radioactive decay of thorium and uranium produce most of our geothermal energy.
LL <–ought to be at work.
*LazarusLong42
Actually, I think that every element lighter than iron will end up in a star at some point. Fusion of these lighter elements (during a star’s death, not the main hydrogen-helium process) produces energy up to the point that iron is made. Making heavier elements takes more energy than is “stored up” in the matter of the heavier element. They’re made during supernovas, where the strict path to entropy is not always followed.
As long as there’s hydrogen in the universe, more stars can be born and the universe stays alive. But once all the lighter elements are fused to form iron, there will be no more energy left in the universe, and the universe will crunch into a massive black hole.
So do I understand this correctly? Is a universe of iron the final end of a collapsing universe model? That sounds almost poetic, in a mind-numbing-terror way…that what I am will become cold, hard iron. (insert Black Sabbath joke here)
And if we have a universe which expands forever, this cannot be the case, true? And in theories of a “Big Crunch”, that is expected to happen long before the elements all turn into iron, is that also true?
Una (who fears cosmology)
Actually, as for the Heat Death of the universe, space will expand forever (no Big Crunch - - which, technically speaking, would not be a black hole) and every atom (including iron) will decay into fundamental particles.
http://itss.raytheon.com/cafe/qadir/q2864.html
http://itss.raytheon.com/cafe/qadir/q2633.html
See my other post re: iron.
As far as fearing cosmology…just keep thinking about the beginning and the middle times…that’s good stuff. 
The end is what gets depressing.
So… the elements in the earth heavier than iron come from the prior life and death of a now (assumedly exploded) star, the remnants of which were floating around and got wound into the accretion disk that eventually formed the earth 4 + billion years ago?
I understand “heat death” to mean the ultimate fate of a static (not expanding or contracting) universe. After all of the usable energy has been converted to heat and the universe reaches thermal equilibrium, there will be no further activity. The universe will be dead. Your second link supports your definition. However, if you look at What exactly is the heat death of the universe… it says that a forever exanding universe will experience a “cold death”.
Yes, We are star dust.
“Heat death” is actually a pretty cold way to go. The key is that, although all of the energy in the Universe is heat, the Universe gets very big, so the energy density is low.
So far as is known, most elements are stable (or at least, the most common isotope is), regardless of whether they’re heavier or lighter than iron. For anything other than iron, there’s some energy that can be released, but it’s not going to actually be released unless you have extreme conditions, like the interior of a star.
Some Theories of Everything which are being tossed around predict that protons eventually decay, with a half-life in the trillions of years. If this happens, then eventually, all matter will be reduced to electrons, neutrinos, photons, and their antiparticles, and depending on how fast the Universe expands, maybe nothing but photons. Don’t wait for it, though… A trillion years is an awfully long time.
Interesting. I had not heard it referred to as “cold death” before. The difference seems slight (two sides of the same coin). Thanks for the link.
Yes. Cool, eh? For that matter (so to speak), every element except hydrogen and helium (and a bit of lithium) was generated by stars. Main sequence stars convert hydrogen/helium up to iron and then the explosive energy of supernovae is needed to slap iron atoms into heavier elements.