If the outermost electron in an atom is excited to a very high energy state, its orbit is far beyond that of the other electrons. To a good approximation, we can think of the electron as orbiting a compact core with a charge equal to the charge of a single proton. The outer electron in such a Rydberg atom thus has energy levels corresponding to those of hydrogen.
a. What is the radius of the state of the Bohr hydrogen atom?
b. Sodium is a common element for such studies. How does the radius you calculated in part a compare to the approximately radius of a typical sodium atom?
The radius of the electron orbit in state is:
The radius from part a) is more then 1000 times bigger then the radius of the sodium atom.