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(a) Figure 8 shows the symbol for the nucleus of an atom of strontium-90 - Edexcel - GCSE Physics - Question 5 - 2020 - Paper 1
Question 5
(a) Figure 8 shows the symbol for the nucleus of an atom of strontium-90. (i) How many protons are in the nucleus of an atom of strontium-90? (ii) How many ne... show full transcript
Worked Solution & Example Answer:(a) Figure 8 shows the symbol for the nucleus of an atom of strontium-90 - Edexcel - GCSE Physics - Question 5 - 2020 - Paper 1
Step 1
Step 2
How many neutrons are in the nucleus of an atom of strontium-90?
Answer
To find the number of neutrons, we subtract the atomic number from the mass number. The mass number for strontium-90 is 90 and the atomic number is 38. Thus, the number of neutrons is: Hence, there are 52 neutrons in strontium-90.
Step 3
Complete the table in Figure 9.
Answer
We know the half-life of strontium-90 is 29 years. After one half-life, the mass reduces from 1600 g to half its value, which is 800 g. After two half-lives, it reduces to half again. Thus, the mass of strontium-90 after 29 years should be 800 g, leading to the completion:
| mass of strontium-90 in g | time in years |
|---|---|
| 1600 | 0 |
| 800 | 29 |
| 400 | 58 |
Step 4
Step 5
How should a teacher ensure safety when using radioactive materials?
Answer
To ensure safety while handling radioactive materials, the teacher should:
- Keep a safe distance from the radioactive source.
- Use shielding to protect against radiation.
- Wear protective clothing and gloves.
- Return the source to storage as soon as the experiment is complete.
Step 6
Describe how to measure the count rate.
Answer
To measure the count rate, follow these steps:
- Take a measurement without the source to determine the background count.
- Position the radioactive source near the detector.
- Measure the distance between the source and the detector.
- Record the count on the detector screen.
- Wait until the background reading stabilizes.
- Use the same time for each count and record each measurement.
- Repeat the measurements until you notice low values.