Talk:Untriseptium

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[edit] Last possible element?

I read that there cannot be any more element past this one (according to our current understanding of physics, of course). May a have an answer on this?
David Latapie (✒ | @) 14:36, 29 September 2006 (UTC)

Solve the equation for a nucleus of atomic number 138, noting that the 1s e- velocity now exceeds the speed of light in a vacuum c, which is a no-no for ordinary particles. Snarfevs 14:58, 9 October 2006 (UTC)

If you view things non-relativistically, there is nothing wrong with exceeding c. If you view things relativistically, you don't use the Schrödinger equation in the first place; you use the Dirac equation. If you mix up non-relativistic and relativistic argumentation, it's no wonder that there will be inconsistencies. Icek (talk) 09:10, 18 December 2007 (UTC)

Does it make any sense to extrapolate the Bohr model to conclude that Z=137 is the limit? Seems that a QED analysis is required. After all, the "velocity of an electron" is non-sensical in an atom. This is a classical notion. 65.119.39.220 20:59, 17 October 2006 (UTC)

I think it make sense, if you speak in terms of energy levels instead of "velocities". The energy level of 1s orbital when Z=137, becomes of the order of the rest mass of the electron or positron (511 keV). The dense electric field near a nucleus with Z >= 137, easily produces electron/positron pairs, with electron capture and positron emission (see "virtual particle" and "pair production" ). Furthermore, the high Coulomb electric repulsive energy within the nucleus needs to be screened by more and more neutrons, which destabilises it (see Why nuclei decay?, see also the growing electrostatic term in the Bethe-Weizsäcker formula). Actually I suspect the effect may appear even before, say from Z > 128, because of the greater value for the Fine Structure Constant at high energy levels. Philip Dalleur Phdalleur 17:48, 10 December 2006 (UTC)