Q24 · 2024 · Paper 1Complex familiar7 marks
QUESTION 24 (7 marks)
The atomic energy level diagram for an unknown multi-electron ion is shown.
a)[4 marks]
Calculate the wavelength of light emitted as electrons move from to . Show your working.
b)[3 marks]
A photon with of energy is incident on the unknown ion and collides with an electron in the first energy level. Explain what would happen within the ion in terms of the photon and electron.
WORKED SOLUTION
7 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
Energy change for the n = 4 to n = 2 transition
V
13.6
3.4
10.2 e
−
=
34
8
19
7
6.626 10
3 10
10.2 1.6 10
1.22 10
E
hf
hc
λ
λ
λ
−
−
−
=
=
×
× ×
×
×
=
=
×
Wavelength =
7
1.22 10
−
×
m
The photon will be absorbed. Since the photon energy of 40.8 eV
corresponds to the difference in energies between the first and
second energy levels, an electron in the first energy level will
absorb the photon and jump to the second energy level in its
excited state.
• calculates the change in energy between
n = 2 and n = 4 energy levels to be 10.2 eV
[1 mark]
• converts between eV and J [1 mark]
• shows mathematical reasoning that
hc
E
λ
=
[1 mark]
• calculates the wavelength [1 mark]
• identifies photon is absorbed by electron
[1 mark]
• explains photon energy as equivalent to the
gap between n = 1 and n = 2 [1 mark]
• explains photon will be absorbed because
electron in n = 1 will jump to n = 2 [1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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