1. Radioactivity

2. ParticleRelative massRelative charge Proton1 Neutron0 Electronalmost zero 1) a)Fill in the labels on the atom. (1 mark) b)Fill in the table with the correct values. (3 marks) Isotopes c) Fill in the blanks for the Hydrogen isotopes. (2 marks)

3. Decay 2) What three types of radioactive decay are there? …………………………………………………………………… ………………………………………………………… (1 mark) 3) Describe each type of decay. 1…………………………………………………………………… …………………………………………………………………….. 2…………………………………………………………………… …………………………………………………………………….. 3…………………………………………………………………… ………………………………………………………… (3 marks) 4) Uranium-230 nuclei emit alpha radiation and become nuclei of thorium (Th). a) Complete the equation. (2 marks) 5) Potassium-40 decays, via Beta emission, to Calcium 40. Write a balanced equation for this decay. (use the periodic table on the next page to help.) ………………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… ………………………………………………………..(3 marks)

5. Detecting radiation Counts in 300 seconds ReadingsAverage No source present10294110 Source present at fixed distance from tube No lead present346634203410 Thick lead plate present10510989 Aluminium sheet in place of thick lead sheet183417871818 The following readings were taken using an unknown source of radiation. 6) a)Complete the table by calculating the average readings. b)What equipment would you use to count the emitted radiation? …………………………………………………………(1 mark) c)Why are the readings on each line not the same? …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………..(2 marks) 7) What can you say, from the table, about the effect on the radiation of: a)The lead plate? …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………..(2 marks)

6. b) The aluminium plate? ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… …………………………………………..(2 marks) 8) Why is it possible to say from the readings that: a) Gamma radiation is emitted by the source? ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… …………………………………………..(2 marks) b) Alpha and beta radiation might be emitted by the source? ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… …………………………………………..(2 marks) 9) What further tests could you make to find out whether or not the source emits alpha radiation? ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… …………………………………………..(2 marks)

7. 10) (a) Uranium-234 (234U) is a radioactive element. The graph shows the number of protons and neutrons in the nuclei of the elements formed when uranium-234 decays. (i) How does the graph show that uranium-234 (234U) and thorium-230 (230Th) emit alpha particles?......................................................................................................... (1 mark) (ii) What makes uranium and thorium different elements?......................................................................................................... (1 mark) (iii) Radioactive decay may also produce gamma radiation. Why does the emission of gamma radiation not cause a new element to be formed?.................................................................................................................................................................................................................. (1 mark)

8. (b) The graph shows how the thickness of different materials needed to absorb 90% of the gamma radiation emitted by a source depends on the energy of the radiation. The energy of the gamma radiation is given in units called electron-volts. (i) Which of the materials shown is least effective at absorbing gamma radiation? Use the information in the graph to give a reason for your answer................................................................................................................................................................................................................... (1 mark) (ii) For gamma radiation of energy 1.5 million electron-volts, how many times more effective is steel than water at absorbing the radiation? Show clearly how you obtain your answer............................................................................................................................................................................................................................................................................................................................ (2 marks)

9. (c) Scientists in the early twentieth century thought that atoms were made up of electrons scattered inside a ball of positive charge. This was called the ‘plum-pudding’ model of the atom. Rutherford and Marsden did an experiment, in which a beam of alpha particles was aimed at a thin sheet of gold. Explain how the results of this experiment led to a new model of the atom. You may include one or more diagrams in your answer....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (3 marks)

10. 11) (a) When an unstable barium nucleus changes into a lanthanum nucleus, a beta particle is emitted. (i) What is a beta particle?.......................................................................................... (1 mark) (ii) How is the nucleus of a lanthanum atom different from the nucleus of a barium atom?................................................................................................................................................................................................... (1 mark) (iii) Describe how a neutral atom may be changed by a collision with a beta particle....................................................................................................................................................................................................(1 mark) (b) The diagram shows how radiation can be used to kill the cells of a brain tumour. Why is a beta emitting radioactive source unsuitable for this purpose?....................................................................................................................................................................................................(1 mark)