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Old 06-11-2019, 10:31 AM
Exapno Mapcase is offline
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How Many "Natural" Elements Are There?


The standard pop sci position is that there are 93 natural elements, through Uranium.

That's not true, though. Both Neptunium and Plutonium have been discovered in nature.

I think that all the smaller elements have been found, but a memory tickles a synapse that some, maybe Technetium, have only been made in labs.

What's the latest word on this? Are there 95 natural elements. More? Fewer?
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Old 06-11-2019, 10:43 AM
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Define "Nature." I.E., do the conditions in a supernova count? Which is, AIUI, how we got all of the elements heavier than Iron in the first place.

I'd add Astatine to the list with Technetium and the heavier Actinides. While At is created naturally via radioactive decay, per the wiki, there's maybe 25 grams on Earth at any one time. As one of my old chemistry professors put it, it's one of those elements where two scientists are staring at an oscilloscope: "Did you see it wiggle?" "Yeah, you did too!?" (Champagne pops) Though I guess enough of it has been made to get at quite a lot of its physical properties.

Last edited by Gray Ghost; 06-11-2019 at 10:45 AM.
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Old 06-11-2019, 10:47 AM
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Looks like Francium is another below-92 element that's pretty much impossible to find 'naturally'.

There have to be others; Astatine was just the first that came to mind. And I didn't know before reading the wiki, that scientists actually hadn't made any significant quantities of the pure element in the lab.
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Old 06-11-2019, 10:51 AM
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Naturally occurring Technetium has been found in trace amounts as a result of naturally occuring fission reactions. Naturally occurring Promethium has been found as a result of rare decays of Europium and Uranium.

Perhaps the problem is the definition of 'naturally occurring'.

In 1962, technetium-99 was isolated and identified in pitchblende from the Belgian Congo in extremely small quantities (about 0.2 ng/kg);[20] there it originates as a spontaneous fission product of uranium-238. The Oklo natural nuclear fission reactor contains evidence that significant amounts of technetium-99 were produced and have since decayed into ruthenium-99.[

There are two possible sources for natural promethium: rare decays of natural europium-151 (producing promethium-147) and uranium (various isotopes).

Last edited by TriPolar; 06-11-2019 at 10:55 AM.
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Old 06-11-2019, 11:08 AM
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Quote:
Originally Posted by Exapno Mapcase View Post
The standard pop sci position is that there are 93 natural elements, through Uranium.
Nitpick: uranium is element 92. There are 92 elements with an atomic number less than or equal to that of uranium.
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Old 06-11-2019, 12:17 PM
Exapno Mapcase is offline
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Quote:
Originally Posted by markn+ View Post
Nitpick: uranium is element 92. There are 92 elements with an atomic number less than or equal to that of uranium.
D'oh!

To answer Gray Ghost, I meant findable on Earth, and not from a lab.

"The Astatine Mines of Tau Ceti 11" is either a plot for an old-fashioned science fiction novel or a really nerdy band name.
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Old 06-11-2019, 03:14 PM
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Well, what trace level of rarity counts as "findable"?
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Old 06-11-2019, 04:19 PM
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And, for that matter, where and when? I'm sure that somewhere out in the universe, at some point, the conditions have been right at some point to have created Einsteinium. That's "in nature", even though it may have been 10,000 light years away and 8 billion years ago.
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Old 06-11-2019, 04:34 PM
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He did say "on Earth", so that clears up that point, at least.
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Old 06-11-2019, 08:02 PM
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It has to be found on Earth, since that's the pop sci way the question is framed. And by "natural" I meant that even an atom of Oganesson would count if if could be identified in a rock somewhere, not made in an accelerator.

(Weird. I was positive I answered this earlier. This is the second time in the past couple of days that I remember posting but nothing appeared. Are other people reporting this, Chronos?)
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