1 2 3 The Future of Post-Human Chemistry: A Preface to a New Theory of Substances ..., de Peter Baofu, page 285 ↑ The problem may actually occur at approximately Element 173, given the finite extension of nuclear-charge distribution. See the article on Extension of the periodic table beyond the seventh period, and the article section Relativistic effects of Atomic orbital. ↑ Duffie, John A.