The Upper Limit of the Periodic Table
The Periodic Table has been acknowledged as one of the most influential keys to understanding modern chemistry. A wealth of information is organized into a readily interpretable array of essential atomic data. Since the days of Dmitri Mendeleev, who is credited with arranging our modern periodic table on the basis of physical similarities, atomic physicists have drastically extended the number of elements by the preparation of artificial elements. These are atoms not found naturally on Earth due to radioactive decay instability but have been created synthetically by atomic bombardment and collisions.
The decade of the 1940’s also marked the creation of the first trans-uranium element. Neptunium was the result of Berkeley scientists Edwin McMillan and Philip Abelson colliding uranium with neutrons as was the concurrent production of element 94, named plutonium in the sequence correlating with the modern group of solar system planets. One name suggested for element 94 was “extremium” offering the proposition that this artificially produced element was the upper limit or heaviest possible atom.
Is there an upper limit to the periodic table? The intrinsic instability with respect to nuclear decay appears to limit the production of elements with atomic numbers greater than that of uranium. Most of the trans-uranium elements have extremely short half-lives and very limited production quantities. Attempting to load the tiny atomic nucleus with 100+ protons appears to provide a barrier that may have reached its synthetic limit.