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Quantum Phenomena - discrete energy levels for electrons

Q4.

(a) When free electrons collide with atoms in their ground state, the atoms can be excited or ionised.

(i) State what is meant by ground state.

(1 mark)

(ii) Explain the difference between excitation and ionisation.

(3 marks)

(b) An atom can also become excited by the absorption of photons. Explain why only photons of certain frequencies cause excitation in a particular atom.

(4 marks)

(c) The ionisation energy of hydrogen is 13.6eV. Calculate the minimum frequency necessary for a photon to cause the ionisation of a hydrogen atom. Give your answer to an appropriate number of significant figures.

(4 marks)

(Total 12 marks)