Atomic line spectra and energy levelsEdexcel A-Level Physics: Flashcards

What these 12 flashcards ask

What is an energy level?
Why are energy levels given negative values?
What is the ground state?
How is a photon produced in an atom?
State the equation linking photon frequency to the energy levels involved.
Why does an emission line spectrum have separate lines?
What does a line spectrum provide evidence for?
What is an absorption line spectrum?
When is a photon absorbed by an atom?
Why do absorption lines appear dark?
How do you convert an energy gap in eV to a frequency?
Where do the dark lines in an absorption spectrum appear compared with the emission lines of the same element?

Exam questions on Atomic line spectra and energy levels

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
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
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

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).