Radioactive elements in the periodic table

[BlaireE]

Hi Science Buddies,
One of my students asked me how many radioactive elements there are in the periodic table. The answer sheet I provided her hyperlinks to a periodic table that shows 37 elements being radioactive. However some websites say there are 38 elements. She found a site that says the 38th element is Bismuth (83 on the table). I'm confused. Is she correct? Thanks

[LeungWilley]

Hi BlaireE,
Based on articles that I am seeing, Bismuth is a barely radioactive element and this characteristics was only discovered in 2003. Here are several articles on the topic:
https://physicsworld.com/a/bismuth-brea ... pha-decay/
https://www.sciencemag.org/news/2003/04 ... after-all#

However, it doesn't appear that the EPA or NIST have accepted this finding yet as of 2017.
https://www.epa.gov/radiation/radioactive-decay

At any rate, I think your student is technically correct with the 38 count and, hopefully, all of the official document will catch up soon.
Willey

[BlaireE]

Hello Willey,
Thanks so much for this information. I will have a good read over it and then talk to my student. It is really good that I can give her the correct answer.
Cheers

[Razgriz05]

Okay, thanks for the explanation, I had run into contradictory explanations as well. I guess it's like how Pluto was considered as a planet, and then wasn't any longer, which means my kids learned there are 8 planets, while I was taught there are 9...