Richard Feynman is said to have invoked relativity to predict the end of the periodic table at element 137. To Feynman, 137 was a “magic number”—it had popped up for no obvious reason elsewhere in physics. His calculations showed that electrons in elements beyond 137 would have to move faster than the speed of light, and thus violate the rules of relativity, to avoid crashing into the nucleus.
https://www.smithsonianmag.com/science-nature/when-will-we-reach-end-periodic-table-180957851/
More are possible in theory, just less and less likely.