$($a$)$ The ionization energy for the outermost electron in a sodium atom is $5\mathrm{.}1$ eV$.$ Use the Bohr model. $($b$)$ Using z$=11$ determine the corresponding value for the radius r of the outermost Bohr orbit. $($c$)$ Using the value calculated in part $($a$),$ determine the corresponding radius r of the outermost bohr orbit