Table 7.1 shows four different nuclei. [Table 7.1]

1. (a)(i)State which two nuclei have the same number of protons.[1]
2. (a)(ii)State which two nuclei have the same number of neutrons.[1]
3. (a)(iii)State which two nuclei have the same number of nucleons.[1]
4. (b)(i)A teacher uses a Geiger-Müller tube and a counter to measure the background radiation in the laboratory. The counter records 20 counts per minute. A radioactive source is then placed in front of the tube and the counter records 420 counts per minute. State what is meant by 'background radiation'.[1]
5. (b)(ii)The measured count rate of 420 counts per minute can be corrected for background radiation. Calculate the corrected count rate from the source. count rate = ........................................................... counts per minute[1]
6. (b)(iii)The radioactive source has a half-life of 45 minutes. Determine the reading on the counter 90 minutes later. reading on counter = ........................................................... counts per minute[2]
7. (b)(iv)Suggest why your answer to (iii) is only an estimate.[1]
8. (c)Fig. 7.1 shows different uses of three different types of radiation. Draw a line on Fig. 7.1 from each use of radiation to the type of radiation used. One line has been drawn for you. Each type of radiation can be used once, more than once or not at all. [Figure 7.1][2]

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