Structured Questions on Atomic Structure
1.
This question is about atomic and nuclear structure and fundamental forces.
In a nuclear model of the atom, most of the atom is regarded as empty space. A tiny nucleus is
surrounded by a number of electrons.
(a)
Outline one piece of experimental evidence that supports this nuclear model of the atom.
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(3)
(b)
Explain why the protons in a nucleus do not fly apart from each other.
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(2)
(c)
In total, there are approximately 1029 electrons in the atoms making up a person. Estimate
the electrostatic force of repulsion between two people standing 100 m apart as a result of
these electrons.
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(4)
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(d)
Estimate the gravitational force of attraction between two people standing 100 m apart.
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(2)
(e)
Explain why two people standing 100 m apart would not feel either of the forces that you
have calculated in parts (c) and (d).
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(2)
(Total 13 marks)
2.
This question is about the nuclear structure of the atom and atomic energy levels.
When the electron was first discovered it led to the idea that an atom consists of a lump of positive
charge in which the electrons are embedded.
In 1912 Geiger and Marsden carried out an experiment to test the validity of this idea. The results
of their experiment in fact suggested that the atom is mostly empty space with an electrically
charged nucleus of relatively large mass occupying only a small amount of space. (This is the
so-called nuclear model of the atom). Their experiment involved “firing” alpha particles at a thin
sheet of gold foil.
(a)
State the nature of an alpha particle.
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(1)
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The diagram below shows a small part of the gold foil with two alpha particles A and B
approaching the foil.
A
B
gold foil
(b)
(i)
Some alpha particle trajectories lead to the idea that most of the atom is empty space.
On the diagram, draw such a trajectory for the alpha particle A.
(1)
(ii)
Some other alpha particle trajectories lead to the idea that the atom has an
electrically charged, relatively massive nucleus. On the diagram, draw such a
trajectory for the alpha particle B.
(1)
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(iii)
Describe briefly how these trajectories lead to the idea of the nuclear model of the
atom.
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(4)
n=
8
In 1914 Niels Bohr suggested that the electrons in an hydrogen atom occupy discrete energy
levels. The diagram below shows some of the principal energy levels.
n=3
n=2
energy
n=1
(c)
(i)
Label with the letter X, the energy level in which an electron will have zero potential
energy.
(1)
(ii)
Explain how the line spectra of atomic hydrogen supports the idea of discrete energy
levels. You may use the diagram above to support your answer.
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(4)
(Total 12 marks)
3.
This question is about line spectra.
(a)
Light is emitted from a gas discharge tube. Outline briefly how the visible line spectrum of
this light may be obtained.
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(2)
The table below gives information relating to three of the wavelengths in the line spectrum of
atomic hydrogen.
(b)
Wavelength / 10–9 m
Photon energy / 10–19 J
1880
1.06
656
3.03
486
4.09
Deduce that the photon energy for the wavelength of 486  10–9 m is 4.09  10–19 J.
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(2)
The diagram below shows two of the energy levels of the hydrogen atom, using data from the
table above. An electron transition between these levels is also shown.
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–2.41 10 –19 J
photon emitted, wavelength = 656 nm
–5.44 10 –19 J
(c)
(i)
On the diagram above, construct the other energy level needed to produce the energy
changes shown in the table above.
(1)
(ii)
Draw arrows to represent the energy changes for the two other wavelengths shown in
the table above.
(1)
(Total 6 marks)
6
4.
This question is about atomic spectra.
An electron undergoes a transition from an atomic energy level of 3.20  10–15 J to an energy level
of 0.32  10–15 J. Determine the wavelength of the emitted photon.
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(Total 3 marks)
5.
This question is about -particle scattering.
In 1913, Geiger and Marsden carried out an experiment in which -particles were fired at a piece
of gold foil. The diagram below shows two such -particles A and B moving toward a gold
nucleus in the directions shown.
A
nucleus
B
nucleus
(a)
On the diagram above, draw possible paths followed by A and B.
(2)
(b)
Explain how a knowledge of the initial KE of -particles such as A enables an upper limit
for the diameter of a nucleus to be estimated.
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(3)
(Total 5 marks)
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6.
This question is about line spectra.
(a)
Light is emitted from a gas discharge tube. Outline briefly how the visible line spectrum of
this light may be obtained.
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(2)
(b)
The table below gives information relating to three of the wavelengths in the line spectrum
of atomic hydrogen.
Wavelength /  10−9m
Photon energy /  10−19 J
1880
1.06
656
3.03
486
4.09
Deduce that the photon energy for the wavelength of 486  10−9 m is 4.09  10−19 J.
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(2)
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(c)
The diagram below shows two of the energy levels of the hydrogen atom, using data from
the table above. An electron transition between these levels is also shown.
(i)
On the diagram above, construct the other energy level needed to produce the energy
changes shown in the table above.
(1)
(ii)
Draw labelled arrows to represent the energy changes for the two other wavelengths
shown in the table above.
(1)
(Total 6 marks)
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