According to the Bohr model, the speed of an electron in a hydrogen-like atom varies with the atomic number Z and the principal quantum number n.
(i) Explain qualitatively why the electron speed increases with Z but decreases with n.
(ii) Show that for uranium (Z=92) an electron in the first orbit would have a speed comparable to the speed of light, and discuss why this indicates a limitation of the non-relativistic Bohr model for very heavy nuclei.