Photographic Periodic Table
I love the periodic table and each time I revisit a site like Web Elements or PeriodicTable.com I discover something new. However, one secret of the elements not discussed there is the question of exactly how many of the elements are ‘naturally-occurring’. It is often stated that there are 92 naturally occurring chemical elements. And that is a good approximation. Unfortunately it is not strictly correct and that kind of thing irritates me. Let me try to explain.
- Elements 43 (Technetium) and 61 (Promethium) do not occur naturally, so that would make for only 90 naturally occurring elements.
- Element 83 (Bismuth) is the heaviest element which has any stable isotopes. All elements with more than 83 protons i.e. Element 84 (Polonium) and beyond have only unstable isotopes.
- [But see this 2021 ‘Corrigendum’ regarding Bismuth]
- It could be argued that the amounts of Element 85(Astatine) and Element 87 (Francium) that exist any time is so low that they only barely ‘occur’ and shouldn’t really be counted. However if one includes these elements then one should also include the transiently created atoms of Elements 93 (Neptunium) and 94(Plutonium) which are created in naturally radioactive rocks from Element 92 (Uranium).
So what is my point? My points is that it would be lovely to have a simple number to say, but nothing is simple. When asked I generally say there are ‘about 100’ naturally occurring elements and leave the details to a later more intense discussion. Anyway. I’m glad I got that off my chest.
24/12/2019: Corrected the atomic number of promethium.
Protons for Breakfast 
October 1, 2010 at 2:39 pm |
About how many of these elements are found in living matter?
December 30, 2010 at 9:22 am |
94 elements as 8th text book kerala state
December 30, 2010 at 12:18 pm |
No. The point of my article is that this is a simple question which does not have a simple answer. It depends on what one means by ‘naturally occurring’.
December 16, 2019 at 5:46 pm |
You mean element 61,promethium, not 65. 🙂
December 24, 2019 at 1:16 pm |
Thanks. I >HATE< making mistakes like that and I appreciate you taking the time to let me know.
January 4, 2020 at 11:15 pm
Any time. Keep in mind that even if we avoid such errors 99.9 percent of the time, we will make 10 mistakes of the sort for every 10 000 words we write.
January 27, 2021 at 2:08 pm |
Bismuth does not have stable isotopes. It has one radioisotope with an extremely long half-life. So long that it was assumed to be stable until 2003: https://www.nature.com/articles/nature01541
January 27, 2021 at 2:26 pm |
Claire,
Thank you for that information and the link. The abstract tells me that the half-life of 209Bi is (1.9 ± 0.2) × 10^19 yr. If we estimate the current age of the universe as being 14 billion years old i.e. 1.4 x 10^10 years old, then the universe has only existed for one billionth of the half-life of 209Bi!
I am astounded that such measurements are possible and grateful to you for letting me know. I will reflect on this nuanced distinction between ‘stable’ and ‘metastable’.
Best wishes
Michael