I'm interested in whether there are a small subset of elements that are by far the most common in a planet's early stages of formation and a wider range are formed slowly over time through chemical reaction, or if a very wide range of the periodic table can be initially found from the start.

Obviously every planet it unique, but I'm asking about whether there's a common scenario / elemental ratio present in the hot cataclysmic early stages of a planet's formation, or rather it's pretty much diverse from the start. Do most elements generally exist in a planet during early formation, or is it a small subset?

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    $\begingroup$ If you mean "stars", this earlier answer may have some useful info and links. $\endgroup$
    – ron
    Jan 17, 2021 at 3:58
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    $\begingroup$ Assuming the planet wasn't created in the Universe's early infancy (say a few hundred million years after the Big Bang), it's more likely that there are less elements on a planet as time goes by. See extinct radionuclides. That is, unless your planet goes on to develop an advanced technological civilisation... $\endgroup$ Jan 17, 2021 at 4:11
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    $\begingroup$ The only process that can create elements on a planet is radioactive decay, but that removes more elements than it creates (and mostly add to the stock of elements already present). But, the mix of elements on the surface of a planet is heavily influenced by geophysical processes which concentrate some in the surface and others in the core. $\endgroup$
    – matt_black
    Jan 17, 2021 at 14:06

1 Answer 1


Elements are not formed through chemical reactions or in planets (except through nuclear decay) . They are formed in stars through nuclear reactions.

Your heavier elements can't even be formed in your typical star. It takes a supernova.

So pretty much everything the planet is made of is there from the start.

  • $\begingroup$ Exception is helium, which is from alfa decay ( as helium of big bang origin escaped ) and beryllium + boron from cosmic ray spalation of nuclei. $\endgroup$
    – Poutnik
    Jan 17, 2021 at 5:21
  • $\begingroup$ Nice answer, also add lead (Pb) which is constantly forming among other radioactive decay products like radon gas. $\endgroup$
    – AChem
    Jan 17, 2021 at 5:43

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