Atomic line spectra and energy levelsEdexcel A-Level Physics: Mind map

Exam questions on Atomic line spectra and energy levels

1. Hydrogen gas at low pressure is excited in a discharge tube. A hydrogen atom has energy levels of −13.6 eV (n = 1, the ground state), −3.40 eV (n = 2), −1.51 eV (n = 3) and −0.85 eV (n = 4).
   Explain why the light from the discharge tube gives a line spectrum rather than a continuous spectrum.2 marks
2. White light is passed through cool mercury vapour and then into a spectrometer. A mercury atom has energy levels of −10.4 eV (the ground state), −5.5 eV, −3.7 eV and −1.6 eV, and the atoms in the vapour are all in the ground state.
   A photon of energy 5.0 eV passes through the vapour. State and explain whether it is absorbed by the mercury atoms.2 marks
3. An atom of element X has its lowest three energy levels at −6.0 eV (the ground state), −2.4 eV and −1.0 eV. A cool gas of X atoms, all in their ground state, is illuminated with photons of several different energies.
   Calculate the frequency of the radiation emitted when an electron in an X atom falls from the −2.4 eV level to the ground state. (h = 6.63 × 10⁻³⁴ J s, e = 1.60 × 10⁻¹⁹ C)3 marks