A fun but off-topic note: "behave the same chemically" is only approximately true. For heavy atoms like the ones discussed in the article, it's basically true. But for hydrogen, adding one neutron doubles its mass and you can get real effects on chemical reaction rates.

https://en.wikipedia.org/wiki/Kinetic_isotope_effect

And of course, an obligatory "In The Pipeline" link on how it's used in drug discovery: https://www.science.org/content/blog-post/isotopes-get-your-...