By Anupum Pant
The Rutherford-Bohr model or simply the Bohr model described the structure of an atom. In it, the nucleus consisted of protons and neutrons, and was positively charged due to the presence of protons in it. Electrons revolved around the nucleus in circular orbits. It was a very simplified description of an atom and served as a good introductory means to teach the structure of an atom. However, several decades back this model was superseded by the Shrodinger model of atom which described the structure of an atom using quantum theory.
The Bohr model fails on many levels – these have been listed here. [Link]
Richard Feynman, using the postulates of Bohr model, argued that the last possible element that could possibly exist would be the one with the atomic number 137. That is to say, no elements greater than atomic number 137 could exist. This argument comes from a simple analysis.
When you consider the Bohr model, and keep filling the nucleus with protons, a point reaches when the charge inside a nucleus becomes very high. In order to maintain a stable orbit around such a high atomic number element, the electrons in the lowest level (having the smallest radius of orbit) would have to move really fast. Or they’d simply crash into the nucleus. When the atomic number reaches more than 137, the calculations using the Bohr model tell you that the lowest electron (1s electron) in such an atom would have to revolve around the nucleus with a speed that would analytically end up being larger than the speed of light – which of course isn’t possible because nothing travels faster than light. So, the element 137 just cannot exist, or so argued Feynman.