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Why does technetium not occur in nature? It is the only element before bismuth to net exist in nature. What's the reason for that?

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  • $\begingroup$ It's radioactive. $\endgroup$
    – Mithoron
    Oct 7 '15 at 13:34
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    $\begingroup$ It's not that big; also, other nuclei, some of which are just a little bit smaller, and some are a little bit bigger, and some are much bigger, are stable. I'd say technetium is a victim of rare coincidence, much like promethium. $\endgroup$ Oct 7 '15 at 13:56
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    $\begingroup$ This is more suited perhaps for Physics SE, where you would get some nuclear physics folks to discuss nuclear structure and stability. And, you would find this: physics.stackexchange.com/questions/40960/… $\endgroup$
    – Jon Custer
    Oct 7 '15 at 14:06
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Technetium does occur in nature. From the Los Alamos page on technetium:

Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial material have been made. Finally in 1962, technetium-99 was isolated and identified in African pitchblende (a uranium rich ore) in extremely minute quantities as a spontaneous fission product of uranium-238 by B.T. Kenna and P.K. Kuroda.

Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars.

The journal article describing the 1962 discovery is Technetium in nature. B. T. Kenna and P. K. Kuroda. Journal of Inorganic and Nuclear Chemistry 26(4) 493-499 (1964).

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While minute quantities of Technetium are present in nature they are always the product of recent synthesis from other elements by nuclear decay (or neutron capture).

The reason why Technetium is so rare is that its most stable isotope has a half-life on only about 4m years. Therefore any that was present at the creation of the planet (about 4,500m years ago) will have decayed a long time ago. The short half life implies that the only reason any can be present in nature now is if there is some ongoing process that creates it. And that is what we find.

Almost all technetium in the current world is created via nuclear reactions either as a by-product of nuclear power or deliberately to be used in medicine.

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  • $\begingroup$ But there is an ongoing process (in Earth), namely spontaneous fission of uranium in pitchblende. Read Todd Minehardt's answer. $\endgroup$ Mar 7 '16 at 2:06
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There is a law in nuclear physics, saying that nature prevents two neighbors isobars (nuclides having same mass but differing by only one proton) from being both stable. One of these nuclides must decay through beta-plus or beta-minus into the other one.

Surprisingly the neighbors of Technetium, namely Molybdenum and Ruthenium are made of a great number of stable isotopes, without any holes in the series of masses. So Technétium has no possibility to get at least one stable isotope.

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