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 65 (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.
- 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.