IB PHYSICS
SL TOPIC 7: Assignment
Atomic & Nuclear Physics
Name: ___________________________________
Total mark:
/42
Time: 62 minutes
Multiple Choice Answers
1.
___________
2.
1.
Which nucleons in a nucleus are involved in the Coulomb interaction and the strong short-range
nuclear interaction?
Coulomb interaction
2.
___________
Strong short-range interaction
A.
protons
protons, neutrons
B.
protons
neutrons
C.
protons
protons
D.
protons, neutrons
neutrons
The nuclear equation below is an example of the transmutation of mercury into gold.
2
199
1 H  80 Hg

197
79 Au
+X
The particle X is a
A.
gamma-ray photon.
B.
helium nucleus.
C.
proton.
D.
neutron.
(Total 1 mark)
1
3.
This question is about the Rutherford model of the atom.
(a)
Most alpha particles used to bombard a thin gold foil pass through the foil without a
significant change in direction. A few alpha particles are deviated from their original
direction through angles greater than 90°. Use these observations to describe the
Rutherford atomic model.
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(5)
2
199
(b) The isotope gold-197 ( 197
79 Au ) is stable but the isotope gold-199 ( 79 Au ) is not.
(i)
Outline, in terms of the forces acting between nucleons, why, for large stable nuclei
such as gold-197, the number of neutrons exceeds the number of protons.
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(3)
199
(ii) A nucleus of 199
79 Au decays to a nucleus of 80 Hg with the emission of an electron
and another particle. State the name of this other particle.
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(1)
(Total 9 marks)
4.
This question is about radioactive decay and binding energy.
(a)
Describe what is meant by radioactive decay.
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(2)
(b)
A nucleus of thallium-206 (Tl-206) undergoes radioactive decay to a nucleus of lead-206
(Pb-206). In the reaction equation below, identify the proton number Z of lead and the
particle x.
206
206
82T  Z Pb 
 x
Z: .................................................................................................................................
x: .................................................................................................................................
(2)
3
(c)
The mass of a Tl-206 nucleus is 191 870 MeV c–2. Determine the binding energy per
nucleon of Tl-206.
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(4)
(d) State why the binding energy of Pb-206 is greater than that of Tl-206.
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(1)
(Total 9 marks)
5.
This question is about decay of radium-226.
(a)
A nucleus of the isotope radium-226 (Ra) undergoes α-decay with a half-life of
1.6 × 103 yr to form a nucleus of radon (Rn).
Define the terms isotope and half-life.
Isotope: ........................................................................................................................
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Half-life: ......................................................................................................................
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(2)
4
(b) Using the grid below, sketch a graph to show how the activity A of a sample of radium-226
(Ra) would be expected to vary with time t over a period of about 5.0 × 103 yr.
The activity of the sample at time t = 0 is A0.
(3)
(c)
The nuclear reaction equation for the decay of radium-226 (Ra) may be written as
226
88 Ra
(i)
 Rn  α
State the value of the proton number and neutron number of the isotope of radon
(Rn).
Proton number: .................................................................................................
Neutron number: ...............................................................................................
(1)
(ii) Outline why the binding energy of Ra is less than that of Rn.
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(2)
5
(d) The following data are available.
mass of Ra
mass of Rn
mass of α
= 226.0254 u
= 222.0175 u
= 4.0026 u
Show that the energy released in the decay of a Ra nucleus is 4.94 MeV.
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(2)
(Total 10 marks)
6.
This question is about α-particle scattering and nuclear processes.
α-particle scattering
Radium-226 decays with the emission of α-particles to radon (Rn).
(a)
Complete the nuclear reaction equation.
226
88 Ra

Rn +
(2)
(b) Experimental evidence that supports a nuclear model of the atom was provided by
α-particle scattering. The diagram represents the path of an α-particle as it approaches and
then recedes from a stationary gold nucleus.
(i)
On the diagram, draw lines to show the angle of deviation of the α-particle.
Label this angle D.
(1)
(ii) The gold nucleus is replaced by another gold nucleus that has a larger nucleon
number. Suggest and explain the change, if any, in the angle D of an α-particle with
the same energy and following the same initial path as in (b)(i).
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(2)
6
(c)
The diagram shows the initial path of an α-particle that approaches the gold nucleus along a
line joining their centres. On the diagram draw the subsequent path of the α-particle.
(1)
Nuclear processes
(d)
The main nuclear process that gives rise to energy emission from the Sun may be simplified
to
4H → He + energy.
(i)
State the name of this nuclear process.
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(1)
(ii) The total mass of four hydrogen (H) nuclei is 6.693 × 10–27 kg and the mass of a
helium (He) nucleus is 6.645 × 10–27 kg. Show that the energy released in this
reaction is 4.3 × 10–12 J.
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(2)
(iii)
The Sun has a radius R of 7.0 × 108 m and emits energy at a rate of 3.9 × 1026 W.
The nuclear reactions take place in the spherical core of the Sun of radius 0.25R. Use
these data and the answer in (d)(ii) to determine the number of nuclear reactions
occurring per cubic metre per second in the core of the Sun.
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(3)
(Total 12 marks)
7