> Is Feynmanium the last chemical element that can physically exist? That is, what are the chemical consequences of having an element with an atomic number abov

> Is Feynmanium the last chemical element that can physically exist? That is, what are the chemical consequences of having an element with an atomic number above 137, whose 1s electrons must travel faster than the speed of light? Just a nitpick, electrons do not travel - they simply exist as a quantum phenomena, with a probability of existing in certain places. That said, as your link also explains, when we take the electron energy into consideration, it seems like there is a limit for "regular" atoms, but beyond that they may simply exhibit weird quantum mechanics. We have no idea.