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4.1 Atomic structure - High demand – Questions
Q1. Two isotopes of carbon are and .
(a) Describe two similarities and one difference in the atomic structure of the two isotopes.
You should refer to the number and type of sub-atomic particles in each isotope.
Similarity 1 _________________________________________________________
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Similarity 2 _________________________________________________________
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Difference __________________________________________________________
___________________________________________________________________ (3)
is a radioactive isotope with a half-life of 5730 years.
(b) A sample of from a fossilised tree gives a count rate of 20 decays per second.
The tree died 17 190 years ago.
Determine what the count rate of the isotope was when the tree died.
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Count rate = ____________________ decays per second (2)
(c) Some molecules in air contain .
Explain how atoms from the air can become part of human cells.
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(Total 10 marks)
Q2. Some small fractures do not show up on an X-ray image.
To see the fracture doctors inject the patient with a radioactive isotope.
The image is formed by detecting radiation as it leaves the body.
The figure below shows an image of a foot after the patient was injected with the radioactive isotope technetium-99.
© Ni Qin/ Getty Images
Technetium-99 emits gamma radiation.
(a) What is gamma radiation?
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___________________________________________________________________ (1)
(b) Explain why a gamma emitter is used.
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___________________________________________________________________ (2)
(c) Technetium-99 has a half-life of 6 hours.
Give the meaning of the term half-life.
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(d) After treatment, hospital equipment may become contaminated.
Describe the level of the hazard associated with contamination with technetium-99.
You should include in your answer a description of how the level of hazard changes over time.
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___________________________________________________________________ (3)
(e) Some of the hospital equipment may also be irradiated during treatment.
Describe how equipment becomes irradiated.
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(f) Why is irradiated equipment not hazardous?
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(Total 9 marks)
Q3.
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When atoms of uranium 238 (U234) decay they produce another radionuclide called thorium 234 (Th234)
Thorium 234 (Th234) decays by emitting beta radiation.
(i) What does beta radiation consist of?
___________________________________________________________________ (1)
(ii) Thorium 234 (Th238) decays to form protactinium 234 (Pa234).
What differences are there between the nucleus of a protactinium 234 (Pa234) atom and the nucleus of a thorium 234 (Th234) atom?
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___________________________________________________________________ (2)
(Total 3 marks)
Q4. The graph shows how the amount of radiation emitted by a sample of the radionuclide uranium 238 (U238) changes as time passes.
(a) What is the half-life of uranium 238 (U238)? (You should show how you obtained your answer. You may do this on the graph if you wish.)
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Answer ___________________ (3)
(b) What fraction (or percentage) of the uranium 238 (U238) atoms will have decayed after 9 billion years?
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___________________________________________________________________ (1)
(c) Uranium 238 (U238) decays through a long series of intermediate radionuclides to stable atoms of the isotope lead 206 (Pb).
A sample of igneous rock contains 3 atoms of uranium 238 (U238) for every atom of lead 206 (Pb206).
(i) The intermediate radionuclides are not important when estimating the age of the rock. Explain why.
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______________________________________________________________ (1)
(ii) Estimate the age of the rock. (You should explain how you obtained your answer.)
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Answer __________________ billion years (3)
(Total 8 marks)
Q5. (a) When an atom of thorium-232 decays, an alpha (α) particle is emitted from the
nucleus. An atom of radium is left behind.
An alpha particle consists of two protons and two neutrons.
We can represent this radioactive decay in a special kind of equation:
Thorium-228 is also radioactive.
Atoms of this isotope also decay by emitting an alpha particle and producing an isotope of radium.
Complete the equation for this decay.
(4)
(b) An atom of radium-228 decays by emitting a beta (β) particle from the nucleus.
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A beta particle is in fact an electron (symbol ).
The effect of this is to change a neutron into a proton.
An atom of actinium remains.
This type of decay can also be represented by an equation:
This isotope of actinium is radioactive.
An atom of actinium-228 also decays by emitting a beta particle.
An isotope of thorium is left behind.
Complete the equation for this decay.
(4)
(c) Thorium-232 eventually decays to the stable isotope lead-208.
All the steps in this process can be shown on a diagram.
(i) Complete the sentences:
During the decay from (A) to (B) a __________ particle is emitted.
During the decay from (B) to (C) a __________ particle is emitted.
During the decay from (E) to (F) a __________ particle is emitted.
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During the decay from (I) to (J) a __________ particle is emitted. (2)
(ii) The table shows how long it takes for half of the atoms of each isotope to decay.
A rock sample contains:
• many atoms of thorium-232
• even more atoms of lead-208
• hardly any atoms of any of the other isotopes shown on the diagram
Explain this as fully as you can.
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______________________________________________________________ (3)
(Total 13 marks)
Q6. (technetium) is produced by the radioactive decay of (molybdenum).
What change occurs in the nucleus of a molybdenum atom when this happens?
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Q7. (a) (i) Describe the structure of alpha particles.
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______________________________________________________________ (2)
(ii) What are beta particles?
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(b) Describe how beta radiation is produced by a radioactive isotope.
___________________________________________________________________ (1)
(Total 4 marks)
Q8. Iodine-131 (131I) is a radioactive isotope used in medicine.
The graph shows how the count rate of a sample of iodine-131 changed over 24 days.
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(i) Use the graph to calculate the half-life of iodine-131. To obtain full marks you should show clearly how you work out your answer.
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Half-life ________________ days (2)
(ii) Iodine-131 is used to destroy cancer cells in the human thyroid gland.
Explain why the length of the half-life of iodine-131 is important in this use.
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___________________________________________________________________ (2)
(Total 4 marks)
Q9. (a) (i) Describe the structure of alpha particles.
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______________________________________________________________ (2)
(ii) What are beta particles?
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(b) Describe how beta radiation is produced by a radioactive isotope.
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(Total 4 marks)
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Q10. Neptunium-237 (237Np) is a radioactive element. The graph shows the numbers of neutrons and protons in the nuclei of the elements formed when 237Np decays.
(a) Use the periodic table on the Data Sheet to identify element X.
___________________________________________________________________ (1)
(b) Why are 233Pa and 233U considered to be different elements?
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___________________________________________________________________ (1)
(c) What type of radiation is released when 237Np decays to form 233Pa?
___________________________________________________________________ (1)
(d) What change takes place in the nucleus when 233Pa changes into 233U?
___________________________________________________________________ (1)
(Total 4 marks)
Q11. The diagram shows a film badge worn by people who work with radioactive materials. The badge has been opened. The badge is used to measure the amount of radiation to which the workers have been exposed.
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(a) The detector is a piece of photographic film wrapped in paper inside part B of the badge. Part A has “windows” as shown.
Complete the sentences below.
When the badge is closed
(i) ____________ radiation and ____________ radiation can pass through the
open window and affect the film. (1)
(ii) Most of the ____________ radiation will pass through the lead window and
affect the film. (1)
(b) Other detectors of radiation use a gas which is ionised by the radiation.
(i) Explain what is meant by ionised.
______________________________________________________________
______________________________________________________________ (1)
(ii) Write down one use of ionising radiation.
______________________________________________________________ (1)
(c) Uranium-238 has a very long half-life. It decays via a series of short-lived radioisotopes to produce the stable isotope lead-204.
Explain, in detail, what is meant by:
(i) half-life,
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______________________________________________________________ (1)
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(ii) radioisotopes.
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______________________________________________________________ (2)
(d) The relative proportions of uranium-238 and lead-204 in a sample of igneous rock can be used to date the rock. A rock sample contains three times as many lead atoms as uranium atoms.
(i) What fraction of the original uranium is left in the rock?
(Assume that there was no lead in the original rock.)
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______________________________________________________________ (1)
(ii) The half-life of uranium-238 is 4500 million years.
Calculate the age of the rock.
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Age __________ million years (2)
(Total 10 marks)
Q12. The diagram below shows the paths of two alpha particles A and B into and out of a thin piece of metal foil.
(a) The paths of the alpha particles depend on the forces on them in the metal.
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Describe the model of the atom which is used to explain the paths of alpha particles aimed at thin sheets of metal foil.
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___________________________________________________________________ (3)
(b) Scientists used to believe that atoms were made up of negative charges embedded in a positive ‘dough’. This is called the ‘plum pudding’ model of the atom. The diagram below shows a model of such an atom.
(i) Explain how the ‘plum pudding’ model of the atom can explain why alpha particle A is deflected through a very small angle.
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______________________________________________________________ (2)
(ii) Explain why the ‘plum pudding’ model of the atom can not explain the large deflection of alpha particle B.
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(c) We now believe that atoms are made up of three types of particles called protons,
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neutrons and electrons.
Complete the table below to show the relative mass and charge of a neutron and an electron. The relative mass and charge of a proton have already been done for you.
PARTICLE RELATIVE MASS RELATIVE CHARGE
proton 1 +1
neutron
electron
(2)
(d) The diagrams below show the nuclei of four different atoms A, B, C and D.
(i) State the mass number of C.
_________________________
(ii) Which two are isotopes of the same element?
__________ and ___________
Explain your answer.
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______________________________________________________________ (4)
(Total 14 marks)
Q13. (a) Complete the table about atomic particles.
ATOMIC PARTICLE RELATIVE MASS RELATIVE CHARGE
proton +1
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neutron 1 0
electron negligible
(2)
(b) Use the Data Sheet to help you to answer some parts of this question.
Read the following passage about potassium.
Potassium is a metallic element in Group 1 of the Periodic Table. It has a proton (atomic) number of 19.
Its most common isotope is potassium-39, ( ).
Another isotope, potassium-40, ( ), is a radioisotope.
(i) State the number of protons, neutrons and electrons in potassium-39.
Number of protons _____________________________________________
Number of neutrons ____________________________________________
Number of electrons ____________________________________________ (2)
(ii) Explain why potassium-40 has a different mass number from potassium-39.
______________________________________________________________ (1)
(iii) What is meant by a radioisotope?
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(iv) Atoms of potassium-40 change into atoms of a different element. This element has a proton (atomic) number of 20 and a mass number of 40.
Name, or give the symbol of, this new element.
______________________________________________________________ (1)
(v) Explain in terms of atomic structure, why potassium-39 and potassium-40 have the same chemical reactions.
______________________________________________________________ (1)
(c) (i) Name a suitable detector that could be used to show that potassium-40 gives out radiation.
______________________________________________________________
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(1)
(ii) Name a disease which can be caused by too much exposure to a radioactive substance such as potassium-40.
______________________________________________________________ (1)
(Total 10 marks)
Q14. The diagram below shows a method of controlling the thickness of paper produced at a paper mill. A radioactive source which emits beta radiation is placed on one side of the paper and a radiation detector is placed on the other.
(a) How will the amount of radiation reaching the detector change as the paper gets thicker?
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___________________________________________________________________ (1)
(b) Explain, as fully as you can:
(i) why a radioactive source which emits alpha (α) radiation could not be used for this application.
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______________________________________________________________ (1)
(ii) why a radioactive source which emits gamma (γ) radiation could not be used for this application.
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______________________________________________________________
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(iii) why a radioactive source which emits beta (β) radiation can be used for this application.
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______________________________________________________________ (2)
(c) Americium-241 is a radioisotope used in smoke detectors. It has a proton number of 95 and a mass number of 241.
How long would it take the americium-241 in a smoke detector to decrease to one eighth of its original number of radioactive atoms?
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Answer = ____________________ (3)
(Total 8 marks)
Q15. Radon is a radioactive gas. Radon makes a major contribution to background radiation levels. Radon atoms decay by the emission of alpha particles.
(a) (i) What is an alpha particle?
______________________________________________________________ (1)
(ii) From which part of the radon atom does the alpha particle come?
______________________________________________________________ (1)
(b) (i) A sample of air contains 40 000 radon atoms. The half-life of radon is four days. Draw a graph to show how the number of radon atoms present in a sample of air will change over a period of 12 days.
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(3)
(ii) After 20 days, how many of the radon atoms from the original sample of air will have decayed? Show clearly how you work out your answer.
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Number of radon atoms decayed = _____________ (3)
(c) Fairly constant concentrations of radon gas have been found in some deep mine shafts.
(i) Suggest why the concentration of radon gas remains fairly constant although the radon gas decays.
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(ii) Explain why the long term exposure to large concentrations of radon gas could be a danger to health.
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______________________________________________________________ (2)
(Total 11 marks)
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Q16. The radioactive isotope, carbon-14, decays by beta (β) particle emission.
(a) What is a beta (β) particle?
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___________________________________________________________________ (1)
(b) Plants absorb carbon-14 from the atmosphere. The graph shows the decay curve for 1 g of carbon-l4 taken from a flax plant.
Use the graph to find the half-life of carbon-l4. You should show clearly on your graph how you obtain your answer.
Half-life = _________________ years. (2)
(c) Linen is a cloth made from the flax plant. A recent exhibition included part of a linen shirt, believed to have belonged to St. Thomas à Becket, who died in 1162. Extracting carbon-14 from the cloth would allow the age of the shirt to be verified.
If 1 g of carbon-14 extracted from the cloth were to give 870 counts in 1 hour, would it be possible for the shirt to have once belonged to St. Thomas à Becket? You must show clearly the steps used and reason for your decision.
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(Total 6 marks)
Q17. (a) The graph shows how a sample of barium-143, a radioactive isotope with a short
half-life, decays with time.
(i) What is meant by the term isotope?
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(ii) What is meant by the term half-life?
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______________________________________________________________
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(iii) Use the graph to find the half-life of barium-143.
Half-life = _______________ seconds (1)
(b) Humans take in the radioactive isotope carbon-14 from their food. After their death, the proportion of carbon-14 in their bones can be used to tell how long it is since they died. Carbon-14 has a half-life of 5700 years.
(i) A bone in a living human contains 80 units of carbon-14. An identical bone taken from a skeleton found in an ancient burial ground contains 5 units of carbon-14. Calculate the age of the skeleton. Show clearly how you work out your answer.
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Age of skeleton = _______________ years (2)
(ii) Why is carbon-14 unsuitable for dating a skeleton believed to be about 150 years old?
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(c) The increased industrial use of radioactive materials is leading to increased amounts of radioactive waste. Some people suggest that radioactive liquid waste can be mixed with water and then safely dumped at sea. Do you agree with this suggestion? Explain the reason for your answer.
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(Total 9 marks)
Q18. Read the information in the box and then answer the questions.
Igneous rocks contain potassium-40. This is a radioactive isotope. It has a half-life of 1300 million years.
Potassium-40 decays into argon-40 which is stable.
Argon escapes from molten rock. Any argon found in an igneous rock must have been produced since the rock solidified.
A sample of an igneous rock has one atom of potassium-40 for every three atoms of argon-40.
(i) What fraction of the potassium-40 has not yet decayed?
___________________________________________________________________ (1)
(ii) Calculate the age of the rock.
___________________________________________________________________
Age of rock = _______________________ million years (1)
(Total 2 marks)
Q19. A beta particle is a high-energy electron.
(i) Which part of an atom emits a beta particle?
___________________________________________________________________ (1)
(ii) How does the composition of an atom change when it emits a beta particle?
___________________________________________________________________ (1)
(Total 2 marks)
Q20. (a) The diagram shows the parts of a smoke detector. The radioactive source emits
alpha particles.
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The alpha particles ionise the air inside the sensor which causes a small electric current. Any smoke getting into the sensor changes the current. The change in current sets the alarm off.
(i) The smoke detector would not work if a radioactive source that emitted only gamma rays was used.
Why not?
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______________________________________________________________ (1)
(ii) Curium-242 is a radioactive isotope with a half-life of 160 days. It emits alpha particles.
Why is curium-242 not suitable for use inside smoke detectors?
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(iii) Curium-242 and curium-244 are two of the isotopes of the element curium.
How is an atom of curium-242 different from an atom of curium-244?
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(b) Sections of steel are often joined by welding them together. The diagram shows how a radioactive source can be used to check for tiny cracks in the weld.
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Cracks in the weld will be shown up on the photographic film below the thick steel plate.
(i) Which type of source, alpha, beta or gamma, should be used to check the weld?
______________________________________________________________ (1)
(ii) Give a reason why the other two types of source cannot be used.
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______________________________________________________________ (1)
(c) The diagram shows a map of a river and its estuary.
Environmental scientists have found that the water flowing into one part of the river estuary is polluted. To find where the pollution is coming from, the scientists use a radioactive isotope, gold-198.
(i) Explain how the gold-198 is used to find where the pollution is coming from.
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______________________________________________________________ (2)
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(ii) The graph shows how the count rate from a sample of gold-198 changes with time.
Use the graph to calculate the half-life of gold-198.
Show clearly on the graph how you obtain your answer.
______________________________________________________________
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Half-life = _______________ days (2)
(Total 9 marks)
Q21. (a) Complete the following table for an atom of uranium-238 ( )
mass number 238
number of protons 92
number of neutrons
(1)
(b) Complete the following sentence.
The name given to the number of protons in an atom is the proton number or the
______________________________ .
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(1)
(c) An atom of uranium-238 ( ) decays to form an atom of thorium-234 ( ).
(i) What type of radiation, alpha, beta or gamma, is emitted by uranium-238?
______________________________________________________________ (1)
(ii) Why does an atom that decays by emitting alpha or beta radiation become an atom of a different element?
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______________________________________________________________ (1)
(Total 4 marks)
Q22. Most elements have some isotopes which are radioactive.
(a) What is meant by the terms:
(i) isotopes
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______________________________________________________________ (1)
(ii) radioactive?
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______________________________________________________________ (1)
(b) The graph shows how the number of nuclei in a sample of the radioactive isotope plutonium-238 changes with time.
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Use the graph to find the half-life of plutonium-238.
Show clearly on the graph how you obtain your answer.
Half-life = ______________ years (2)
(c) The Cassini spacecraft launched in 1997 took seven years to reach Saturn.
The electricity to power the instruments on board the spacecraft is generated using the heat produced from the decay of plutonium-238.
(i) Plutonium-238 decays by emitting alpha particles.
What is an alpha particle?
______________________________________________________________ (1)
(ii) During the 11 years that Cassini will orbit Saturn, the output from the generators will decrease.
Explain why.
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______________________________________________________________ (2)
(d) Plutonium-238 is highly dangerous. A tiny amount taken into the body is enough to kill a human.
(i) Plutonium-238 is unlikely to cause any harm if it is outside the body but is likely to kill if it is inside the body.
Explain why.
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______________________________________________________________ (2)
(ii) In 1964, a satellite powered by plutonium-238 was destroyed, causing the release of radioactive material into the atmosphere.
Suggest why some environmental groups protested about the launch of Cassini.
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______________________________________________________________ (1)
(Total 10 marks)
Q23. (a) Some rocks inside the Earth contain uranium-238, a radioactive isotope of uranium.
When an atom of uranium-238 decays, it gives out radiation and changes into a thorium-234 atom.
(i) What type of radiation is emitted when a uranium-238 atom decays?
______________________________________________________________ (1)
(ii) From which part of a uranium-238 atom is the radiation emitted?
______________________________________________________________ (1)
(iii) Uranium-235 is another isotope of uranium.
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How is an atom of uranium-235 similar to an atom of uranium-238?
______________________________________________________________ (1)
(b) Uranium-238 has a half-life of 4500 million years.
(i) When the Earth was formed, there was twice as much uranium-238 in the rocks as there is now.
What is the age of the Earth?
______________________________________________________________ (1)
(ii) Complete the graph to show how the number of nuclei in a sample of uranium-238 will change with time. Initially, there were 100 000 nuclei in the sample.
(2)
(Total 6 marks)
Q24. (a) Carbon has three naturally occurring isotopes. The isotope, carbon-14, is
radioactive. An atom of carbon-14 decays by emitting a beta particle.
(i) Complete the following sentences.
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The atoms of the three carbon isotopes are the same as each other because
______________________________________________________________
The atoms of the three carbon isotopes are different from each other because
______________________________________________________________ (2)
(ii) What is a beta particle and from what part of an atom is it emitted?
______________________________________________________________
______________________________________________________________ (1)
(b) Carbon-14 is constantly being made in the atmosphere, yet for most of the last million years, the amount of carbon-14 in the atmosphere has not changed.
How is this possible?
___________________________________________________________________
___________________________________________________________________ (1)
(c) Trees take in carbon-12 and carbon-14 from the atmosphere. After the tree dies, the proportion of carbon-14 that the tree contains decreases.
Graph A shows the decay curve for carbon-14.
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(i) Lake Cuicocha in Ecuador was formed after a volcanic eruption. Carbon taken from a tree killed by the eruption was found to have a count rate of 10.5 counts per minute. At the time of the eruption, the count rate would have been 16 counts per minute.
Use graph A to find the age of Lake Cuicocha.
Age of Lake Cuicocha = _______________________ years (1)
(ii) Finding the age of organic matter by measuring the proportion of carbon-14 that it contains is called carbon dating. This technique relies on the ratio of carbon-14 to carbon-12 in the atmosphere remaining constant. However, this ratio is not constant so the age found by carbon dating needs to be adjusted.
Graph B is used to adjust the age of an object found by carbon dating. The value obtained from graph B will be no more than 50 years different to the true age of the object.
Use graph B and the information above to find the maximum age that Lake Cuicocha could be.
Show clearly how you obtain your answer.
______________________________________________________________
______________________________________________________________
Maximum age of Lake Cuicocha = _______________ years (2)
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(Total 7 marks)
Q25. The diagram shows a system used to control the thickness of aluminium foil as it is being rolled. A radiation source and detector are used to monitor the thickness of the foil.
(a) Which type of source, alpha, beta or gamma, should be used in this control system?
_______________________
Explain why each of the other two types of source would not be suitable.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (3)
(b) The chart shows how the count rate recorded by the detector varies over a short period of time.
Use the graph to explain how the thickness of the foil changes, and how the control system responds to this change.
___________________________________________________________________
___________________________________________________________________
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___________________________________________________________________
___________________________________________________________________ (2)
(c) When first used, the radiation source contains 6 micrograms of strontium-90. The graph shows how the mass of the strontium-90 will decrease as the nuclei decay.
The control system will continue to work with the same source until 75 % of the original strontium-90 nuclei have decayed.
After how many years will the source need replacing?
Show clearly your calculation and how you use the graph to obtain your answer.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Number of years = ____________________ (2)
(Total 7 marks)
Q26. (a) Atoms of the isotope bismuth-212 decay by emitting either an alpha particle or a
beta particle. The equation represents what happens when an atom of bismuth-212 decays by beta emission into an atom of polonium-212.
(i) The bismuth atom and the polonium atom have the same mass number (212).
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What is the mass number of an atom?
______________________________________________________________ (1)
(ii) Beta decay does not cause the mass number of an atom to change.
Explain why not.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________ (2)
(b) When an atom of bismuth-212 emits an alpha particle, the atom decays into an atom of thallium.
An alpha particle is the same as a helium nucleus. The symbol below represents an alpha particle.
(i) The equation below represents the alpha decay of bismuth-212.
Complete the equation by writing the correct number in each of the two boxes.
(2)
(ii) It is impossible for the alpha decay of bismuth-212 to produce the same element as the beta decay of bismuth-212.
Explain why.
______________________________________________________________
______________________________________________________________
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______________________________________________________________ (2)
(Total 7 marks)
Q27. The ‘plum pudding’ model of the atom was used by scientists in the early part of the 20th century to explain atomic structure.
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(a) Those scientists knew that atoms contained electrons and that the electrons had a negative charge. They also knew that an atom was electrically neutral overall.
What did this allow the scientists to deduce about the ‘pudding’ part of the atom?
___________________________________________________________________
___________________________________________________________________ (1)
(b) An experiment, designed to investigate the ‘plum pudding’ model, involved firing alpha particles at a thin gold foil.
If the ‘plum pudding’ model was correct, then most of the alpha particles would go straight through the gold foil. A few would be deflected, but by less than 4°.
The results of the experiment were unexpected. Although most of the alpha particles did go straight through the gold foil, about 1 in every 8 000 was deflected by more than 90°.
Why did this experiment lead to a new model of the atom, called the nuclear model, replacing the ‘plum pudding’ model?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (1)
(c) The diagram shows the paths, A, B and C, of three alpha particles. The total number of alpha particles deflected through each angle is also given.
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(i) Using the nuclear model of the atom, explain the three paths, A, B and C.
A ____________________________________________________________
______________________________________________________________
B ____________________________________________________________
______________________________________________________________
C ____________________________________________________________
______________________________________________________________ (3)
(ii) Using the nuclear model, the scientist E. Rutherford devised an equation to predict the proportion of alpha particles that would be deflected through various angles.
The results of the experiment were the same as the predictions made by Rutherford.
What was the importance of the experimental results and the predictions being the same?
______________________________________________________________
______________________________________________________________ (1)
(Total 6 marks)
Q28. (a) The chart gives the number of protons and neutrons within the nuclei of 7 different
atoms, A – G.
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Which of these atoms are isotopes of the same element?
___________________________________________________________________
Give a reason for your answer.
___________________________________________________________________
___________________________________________________________________ (2)
(b) Radium-226 is a radioactive isotope that decays into radon gas by emitting alpha particles.
The decay can be represented by the equation below.
(i) Complete the equation by writing the correct number in each of the boxes. (2)
(ii) A sample of radium-226 has a count rate of 400 counts per second. The half-life of radium-226 is 1600 years.
How long will it be before the count rate has fallen to 50 counts per second?
Show clearly how you work out your answer.
______________________________________________________________
______________________________________________________________
______________________________________________________________
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Length of time = _______________ years (2)
(c) In 1927, a group of women who had been employed to paint watch faces with a luminous paint sued their former employer over the illnesses caused by the paint. The women had been told that the paint, which contained radium, was harmless.
The company owners and the scientists working for the company knew that radium was harmful and took precautions to protect themselves from the radiation. The women were given no protection.
What important issue did the treatment of the women by the company owners and scientists raise?
Draw a ring around your answer.
economic environmental ethical social
Give a reason for your answer.
___________________________________________________________________
___________________________________________________________________ (2)
(d) In the 1920s, many people, including doctors, thought that radium could be used as a treatment for a wide range of illnesses. Medical records that suggested radium could be harmful were generally ignored. When some of the women who had used the luminous paint died, their deaths were not blamed on radium.
Suggest a reason why the evidence suggesting that radium was harmful was generally ignored.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (1)
(Total 9 marks)
Q29. In 2011 an earthquake caused severe damage to a nuclear power station in Japan.
The damage led to the release of large amounts of radioactive iodine-131 into the atmosphere.
(a) The table gives some information about an atom of iodine-131 .
Complete the table.
mass number 131
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number of protons 53
number of neutrons
(1)
(b) Complete the sentence.
The number of protons in an atom is called the proton number or
the _______________ number. (1)
(c) An atom of iodine-131 decays into an atom of xenon (Xe) by emitting a beta particle.
(i) The decay of iodine-131 can be represented by the equation below.
Complete the equation by writing the correct number in each of the two boxes.
(2)
(ii) A sample of rainwater contaminated with iodine-131 gives a count rate of 1200 counts per second.
Calculate how many days it will take for the count rate from the sample of rainwater to fall to 75 counts per second.
Half-life of iodine-131 = 8 days
Show clearly how you work out your answer.
______________________________________________________________
______________________________________________________________
_______________ days (2)
(iii) If people drink water contaminated with iodine-131, the iodine-131 builds up in the thyroid gland. This continues until the thyroid is saturated with iodine-131 and cannot absorb any more. The radiation emitted from the iodine-131 could cause cancer of the thyroid.
In Japan, people likely to be drinking water contaminated with iodine-131 were advised to take tablets containing a non-radioactive isotope of iodine.
Suggest why this advice was given.
______________________________________________________________
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______________________________________________________________
______________________________________________________________
______________________________________________________________ (2)
(Total 8 marks)
Q30. Many countries use nuclear power stations to generate electricity. Nuclear power stations use the process of nuclear fission to release energy.
(a) (i) What is nuclear fission?
______________________________________________________________
______________________________________________________________ (1)
(ii) Plutonium-239 is one substance used as a fuel in a nuclear reactor. For nuclear fission to happen, the nucleus must absorb a particle.
What type of particle must be absorbed?
______________________________________________________________ (1)
(b) Nuclear fusion also releases energy. Nuclear fusion happens at very high temperatures. A high temperature is needed to overcome the repulsion force between the nuclei.
(i) Why is there a repulsion force between the nuclei of atoms?
______________________________________________________________
______________________________________________________________ (1)
(ii) Where does nuclear fusion happen naturally?
______________________________________________________________ (1)
(c) In 1991, scientists produced the first controlled release of energy from an experimental nuclear fusion reactor. This was achieved by fusing the hydrogen isotopes, deuterium and tritium.
Deuterium is naturally occurring and can easily be extracted from seawater. Tritium can be produced from lithium. Lithium is also found in seawater.
The table gives the energy released from 1 kg of fusion fuel and from 1 kg of fission fuel.
Type of fuel Energy released from 1 kg of fuel in joules
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Fusion fuel 3.4 × 1014
Fission fuel 8.8 × 1013
(i) Suggest two advantages of the fuel used in a fusion reactor compared with plutonium and the other substances used as fuel in a fission reactor.
1. ____________________________________________________________
______________________________________________________________
______________________________________________________________
2. ____________________________________________________________
______________________________________________________________
______________________________________________________________ (2)
(ii) Some scientists think that by the year 2050 a nuclear fusion power station capable of generating electricity on a large scale will have been developed.
Suggest one important consequence of developing nuclear fusion power stations to generate electricity.
______________________________________________________________
______________________________________________________________
______________________________________________________________ (1)
(d) Tritium is radioactive.
After 36 years, only 10 g of tritium remains from an original sample of 80 g.
Calculate the half-life of tritium.
Show clearly how you work out your answer.
___________________________________________________________________
___________________________________________________________________
Half-life = __________________ years (2)
(Total 9 marks)
Q31. Atoms are different sizes.
One of the heaviest naturally occurring stable elements is lead.
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Two of its isotopes are lead-206 ( ) and lead-208 ( ).
(a) (i) What is meant by ‘isotopes’?
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________ (2)
(ii) How many protons are in the nucleus of a atom?
__________________ (1)
(iii) How many neutrons are in the nucleus of a atom?
__________________ (1)
(b) A nucleus can be accelerated in a particle accelerator and directed at a large nucleus. This produces a heavy nucleus that will decay after a short time.
This is shown in Figure 1.
(i) In 1984, nuclei of iron (Fe) were directed at nuclei of lead (Pb). This produced nuclei of hassium (Hs).
Complete the equation for this reaction by writing numbers in the empty boxes.
(3)
(ii) Use the correct answer from the box to complete the sentence.
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an electron a proton a neutron
The particle X in part (b)(i) is _________________________________ . (1)
(iii) After acceleration the iron nuclei travel at a steady speed of one-tenth of the speed of light.
The speed of light is 3.00 × 108 m/s.
Calculate the time taken for the iron nuclei to travel a distance of 12 000 m.
______________________________________________________________
______________________________________________________________
Time taken = ____________________ s (2)
(iv) Linear accelerators, in which particles are accelerated in a straight line, are not used for these experiments. Circular particle accelerators are used.
Suggest why.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________ (3)
(c) Hassium-265 ( ) decays by alpha emission with a half-life of 0.002 seconds.
(i) What is meant by ‘half-life’?
Tick ( ) two boxes.
Tick ( )
The average time for the number of nuclei to halve
The time for count rate to be equal to background count
The time for background count to halve
The time for count rate to halve
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(2)
(ii) Complete the equation for the decay of Hs-265 by writing numbers in the empty boxes.
(2)
(d) The table below shows how the atomic radius of some atoms varies with atomic number.
Atomic number
Atomic radius in picometres (pm)
15 100
35 115
50 130
70 150
95 170
1 pm = 10–12 m
(i) On Figure 2, use the data from the table above to plot a graph of atomic radius against atomic number and draw a line of best fit.
Two points have been plotted for you.
Figure 2
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(2)
(ii) Scientists believe that the element with atomic number 126 can be produced and that it will be stable.
Use your graph in Figure 2 to predict the atomic radius of an atom with atomic number 126.
Atomic radius = ____________________ pm (1)
(Total 20 marks)
Q32. The figure below shows how the activity of a radioactive isotope changes over an 8 hour period of time.
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(a) Predict how long it will take for the count rate to fall from 100 to 1.56 Bequerels.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Time = _______________ hours (2)
(b) Lead-210 is a radioactive isotope that decays to an isotope of mercury by alpha decay.
Complete the nuclear equation to show the alpha decay of lead-210.
(3)
(c) Explain how ionising radiation can have hazardous effects on the human body.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
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(5) (Total 10 marks)
Q33. Atoms are very small and most of their mass is concentrated in the nucleus.
Electrons orbit at different distances from the nucleus.
(a) A nucleus is much smaller than an atom.
Approximately how many times smaller is a nucleus than an atom?
Tick one box.
100
1000
10 000
100 000
(1)
(b) The electrons in an atom can only orbit at specific distances from the nucleus.
State what causes an electron’s distance from the nucleus to increase or decrease.
Increase ___________________________________________________________
___________________________________________________________________
Decrease __________________________________________________________
___________________________________________________________________ (2)
(c) Atoms have different atomic numbers and mass numbers.
In terms of sub-atomic particles, describe the difference between an atom’s atomic number and its mass number.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (2)
(d) Transmutation is the name given to a process where one element changes into
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another.
Explain and compare how two different types of radioactive decay can cause transmutation.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (4)
(Total 9 marks)
Q34. There are many different isotopes of gold. The isotope, gold-198, is radioactive. An atom of gold-198 decays by emitting a beta particle.
(a) Complete the following sentences.
All atoms of gold have the same number of ________________________________
and the same number of __________________________________ .
The atoms from different isotopes of gold have different numbers of ____________ .
A beta particle is an __________________________________ emitted
from the __________________________________ of an atom. (3)
(b) The graph shows how the count rate from a sample of gold-198 changes with time.
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Time in days
Use the graph to calculate the half-life of gold-198.
Show clearly on the graph how you obtain your answer.
___________________________________________________________________
___________________________________________________________________
Half-life = ________________ days (2)
(c) The diagram shows a map of a river and the river estuary.
Environmental scientists have found that water flowing into one part of the river estuary is polluted. To find where the pollution is coming from, the scientists use a radioactive isotope, gold-198.
The gold-198 is used to find where the pollution is coming from.
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Explain how.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (2)
(Total 7 marks)
Q35. In the early part of the 20th century, scientists used the ‘plum pudding’ model to explain the structure of the atom.
Following work by Rutherford and Marsden, a new model of the atom, called the ‘nuclear’ model, was suggested.
Describe the differences between the two models of the atom.
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________ (Total 4 marks)
