Unsepttrium

Unsepttrium (), also called dvi-francium , eka-Ununennium, or element 173, is a possible chemical element which has never been seen in nature, and it has never been made. It is not known if this element is possible, as the instabilities may show that the periodic table ends soon after the island of stability at unbihexium; but it is likely the heaviest possible neutral element.  Its atomic number is 173 and its atomic symbol is Ust.

The name unsepttrium is a temporary IUPAC systematic element name.

 Significance 
Although Richard Feynman said that a simple interpretation of the relativistic Dirac equation runs into problems with electron orbitals at Z > 1/α = 137, that probably means that neutral atoms cannot exist beyond untriseptium, and that a periodic table of elements based on electron orbitals stops at this point, a deeper analysis shows the limit to be Z ≈ 173, meaning that neutral atoms most likely cannot exist with an atomic number greater than 173.See Extended periodic table and untriseptium.  This makes unsepttrium theoretically the heaviest neutral element possible.

 Related pages 
 untriseptium

 References 

Category:Hypothetical chemical elements