Radioactivity Calculations IGCSE
Measuring Radioactivity
1.
Mr. Snewin measures the background radiation level in S2 and records the following results.
Experiment Number
Activity
1
15 counts per minute.
2
11 counts per minute.
3
13 counts per minute.
a. Calculate the average reading for the background radiation level.
b. Mr. Snewin then records the activity of a sample of strontium-90. The reading is 309 counts per
minute. Calculate the corrected activity of the sample of strontium-90.
Alpha Decay
Complete the following equations for alpha decay:
A
Z
Xe  Z-2 Yr + 2He
A-4
4
1. 238
92
Ur  88 Th + 2 He
4. 242
94
Pu  92 Ur + 2 He
2. 251
98
Cf  96Cm + 2 He
5. 174
72
Hf  70 Yb + 2 He
3. 211
83
Bi  Tl + He
6. 190
78
4
Pt  186
76Os + 2 He
234
4
247
207
81
4
4
2
Beta Decay
Complete the following equations for beta decay:
238
170
4
4
3A
Z
Xu  Z+1 Ye + -1 e
3
1
Hu  2 He + -1 e
A
0
14
6
Cr  7Ng + -1e
4.
2. 137
55
Cs  56 Ba + -1e
5. 40
19
Kf  20Ca + -1 e
3. 60
27
Co  28 Ni + -1 e
6. 32
15
Pt  3216Ss + -10e
1.
14
137
60
0
0
0
Gamma Decay
Complete the example equation for gamma decay:
3A
Z
3
40
0
0
Xu  Z Ye + 0 γ
A
0
Radioactivity Calculations IGCSE
Half Life
Calculate the half lives of the following samples.
1. A sample of iodine-123 whose activity falls from 1000 Bq to 250 Bq in 14.4 hours.
2. A sample of technetium-99m whose activity falls from 200 Bq to 25 Bq in 18 hours.
3. A sample of strontium-90 whose activity falls from 500 Bq to 62.5 Bq in 86.4 years.
Calculate the how long it would take for the following to decay to an activity of 1 Bq.
4. A sample of cobalt-60 (half life – 5.27 years) whose original activity is 64 Bq.
5. A sample of iodine-131 (half life – 8 days) whose original activity is 128 Bq.
6. A sample of polonium-210 (half life – 138 days) whose original activity falls is 32 Bq.
Nuclear Fission
1.
2.
3.
4.
5.
Assuming all three of the neutrons released from each fission reaction goes on to react, how many
uranium-235 nuclei will split after...
the first reaction?
the second reaction?
the third reaction?
the fourth reaction?
the fifth reaction?
In which generation of reactions will you get...
1. 59,049 splits?
2. 1,594,323 splits?
3. 129,140,163 splits?