7 (a) Which of these describes isotopes of an element?
A - Edexcel - GCSE Physics - Question 7 - 2020 - Paper 1
Question 7
7 (a) Which of these describes isotopes of an element?
A.
B.
C.
D.
(b) Figure 9 represents a decay that can happen inside the nucleus of an atom.
Which decay is r... show full transcript
Worked Solution & Example Answer:7 (a) Which of these describes isotopes of an element?
A - Edexcel - GCSE Physics - Question 7 - 2020 - Paper 1
Step 1
Which of these describes isotopes of an element?
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Answer
The correct answer is A: same atomic number, different number of neutrons. This means that isotopes of an element have the same number of protons (atomic number) but differ in the number of neutrons.
Step 2
Which decay is represented in Figure 9?
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Answer
The decay represented in Figure 9 is C: beta plus. In beta plus decay, a proton is converted into a neutron and a positron is emitted.
Step 3
Estimate the activity of this source in the year 2020.
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Answer
The half-life of cobalt-60 is 5 years, so it undergoes 4 half-lives from 2000 to 2020 (20 years).
To find the fraction of original activity, we calculate:
rac{1}{2^4} = rac{1}{16}
Thus, the activity in 2020 is:
38.5 ext{ kBq} imes rac{1}{16} = 2.4 ext{ kBq}
The estimated activity of the source in the year 2020 is 2.4 kBq.
