1. The problem statement, all variables and given/known data The emission spectrum of thermally excited sodium atoms practically consists of a single intensive line at 589 nm wavelength. What is the energy difference (in eV units) between the excited and ground states of the sodium atom? 2. Relevant equations E = hc/lambda, we also know that electron electric charge = 1.6 * 10-19 3. The attempt at a solution I know that the energy of a photon emitted from an excitation of an electron is E = hc/lamda and by dividing that result by the electric charge of the electron, i get the eV units, but I do not understand the ground state and excited states.