Find the frequency of light that corresponds to photons of energy $5.0 \times 10^{-5} \ erg$.

The ratio of the radii of the first three Bohr orbits is:

$(i)$ What is the energy of an electron for hydrogen in $J \ atom^{-1}$ and $J \ mol^{-1}$?
$(ii)$ Calculate the energy of this electron per mole for the first transition ($n=1$ to $n=2$).
$(iii)$ Calculate the ionization energy of hydrogen.

Explain: "Rutherford's atomic model cannot explain the stability of an atom."

If the ionization energy of $He^{+}$ is $8.68 \times 10^{-18} \ J$,then the energy of $Be^{3+}$ ion in the second orbit is:- ($Z$ of $Be = 4$)

What is the potential energy of the electron in the $L$ shell of the hydrogen atom? (in $eV$)