ScienceAges 16-18

Protons, neutrons & mass number

Calculate an atom’s mass number from its proton and neutron counts. This is not relative atomic mass. Review suitability for your learners before teaching.

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Worksheet StudioPractice pack · Ages 16-18

Protons, neutrons & mass number

Take your time. Show your thinking.

1. An atom has 8 protons and 29 neutrons. What is its mass number?
8 p⁺ · 29 n⁰ · A = Z + N = ?
2. An atom has 18 protons and 20 neutrons. What is its mass number?
18 p⁺ · 20 n⁰ · A = Z + N = ?
3. An atom has 16 protons and 23 neutrons. What is its mass number?
16 p⁺ · 23 n⁰ · A = Z + N = ?
4. An atom has 8 protons and 26 neutrons. What is its mass number?
8 p⁺ · 26 n⁰ · A = Z + N = ?
5. An atom has 1 protons and 18 neutrons. What is its mass number?
1 p⁺ · 18 n⁰ · A = Z + N = ?
6. An atom has 14 protons and 7 neutrons. What is its mass number?
14 p⁺ · 7 n⁰ · A = Z + N = ?
7. An atom has 17 protons and 22 neutrons. What is its mass number?
17 p⁺ · 22 n⁰ · A = Z + N = ?
8. An atom has 20 protons and 4 neutrons. What is its mass number?
20 p⁺ · 4 n⁰ · A = Z + N = ?
9. An atom has 19 protons and 9 neutrons. What is its mass number?
19 p⁺ · 9 n⁰ · A = Z + N = ?
10. An atom has 4 protons and 12 neutrons. What is its mass number?
4 p⁺ · 12 n⁰ · A = Z + N = ?
11. An atom has 16 protons and 26 neutrons. What is its mass number?
16 p⁺ · 26 n⁰ · A = Z + N = ?
12. An atom has 20 protons and 11 neutrons. What is its mass number?
20 p⁺ · 11 n⁰ · A = Z + N = ?

12 questions · Seed 45 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 16-18

Protons, neutrons & mass number

Answers and reasoning. Review before teaching.

1. An atom has 8 protons and 29 neutrons. What is its mass number?
37
Mass number counts protons and neutrons: 8 + 29 = 37.
2. An atom has 18 protons and 20 neutrons. What is its mass number?
38
Mass number counts protons and neutrons: 18 + 20 = 38.
3. An atom has 16 protons and 23 neutrons. What is its mass number?
39
Mass number counts protons and neutrons: 16 + 23 = 39.
4. An atom has 8 protons and 26 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 8 + 26 = 34.
5. An atom has 1 protons and 18 neutrons. What is its mass number?
19
Mass number counts protons and neutrons: 1 + 18 = 19.
6. An atom has 14 protons and 7 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 14 + 7 = 21.
7. An atom has 17 protons and 22 neutrons. What is its mass number?
39
Mass number counts protons and neutrons: 17 + 22 = 39.
8. An atom has 20 protons and 4 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 20 + 4 = 24.
9. An atom has 19 protons and 9 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 19 + 9 = 28.
10. An atom has 4 protons and 12 neutrons. What is its mass number?
16
Mass number counts protons and neutrons: 4 + 12 = 16.
11. An atom has 16 protons and 26 neutrons. What is its mass number?
42
Mass number counts protons and neutrons: 16 + 26 = 42.
12. An atom has 20 protons and 11 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 20 + 11 = 31.

12 questions · Seed 45 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 16-18

Protons, neutrons & mass number

Take your time. Show your thinking.

1. An atom has 8 protons and 29 neutrons. What is its mass number?
8 p⁺ · 29 n⁰ · A = Z + N = ?
2. An atom has 18 protons and 20 neutrons. What is its mass number?
18 p⁺ · 20 n⁰ · A = Z + N = ?
3. An atom has 16 protons and 23 neutrons. What is its mass number?
16 p⁺ · 23 n⁰ · A = Z + N = ?
4. An atom has 8 protons and 26 neutrons. What is its mass number?
8 p⁺ · 26 n⁰ · A = Z + N = ?
5. An atom has 1 protons and 18 neutrons. What is its mass number?
1 p⁺ · 18 n⁰ · A = Z + N = ?
6. An atom has 14 protons and 7 neutrons. What is its mass number?
14 p⁺ · 7 n⁰ · A = Z + N = ?
7. An atom has 17 protons and 22 neutrons. What is its mass number?
17 p⁺ · 22 n⁰ · A = Z + N = ?
8. An atom has 20 protons and 4 neutrons. What is its mass number?
20 p⁺ · 4 n⁰ · A = Z + N = ?
9. An atom has 19 protons and 9 neutrons. What is its mass number?
19 p⁺ · 9 n⁰ · A = Z + N = ?
10. An atom has 4 protons and 12 neutrons. What is its mass number?
4 p⁺ · 12 n⁰ · A = Z + N = ?
11. An atom has 16 protons and 26 neutrons. What is its mass number?
16 p⁺ · 26 n⁰ · A = Z + N = ?
12. An atom has 20 protons and 11 neutrons. What is its mass number?
20 p⁺ · 11 n⁰ · A = Z + N = ?

12 questions · Seed 45 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 16-18

Protons, neutrons & mass number

Answers and reasoning. Review before teaching.

1. An atom has 8 protons and 29 neutrons. What is its mass number?
37
Mass number counts protons and neutrons: 8 + 29 = 37.
2. An atom has 18 protons and 20 neutrons. What is its mass number?
38
Mass number counts protons and neutrons: 18 + 20 = 38.
3. An atom has 16 protons and 23 neutrons. What is its mass number?
39
Mass number counts protons and neutrons: 16 + 23 = 39.
4. An atom has 8 protons and 26 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 8 + 26 = 34.
5. An atom has 1 protons and 18 neutrons. What is its mass number?
19
Mass number counts protons and neutrons: 1 + 18 = 19.
6. An atom has 14 protons and 7 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 14 + 7 = 21.
7. An atom has 17 protons and 22 neutrons. What is its mass number?
39
Mass number counts protons and neutrons: 17 + 22 = 39.
8. An atom has 20 protons and 4 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 20 + 4 = 24.
9. An atom has 19 protons and 9 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 19 + 9 = 28.
10. An atom has 4 protons and 12 neutrons. What is its mass number?
16
Mass number counts protons and neutrons: 4 + 12 = 16.
11. An atom has 16 protons and 26 neutrons. What is its mass number?
42
Mass number counts protons and neutrons: 16 + 26 = 42.
12. An atom has 20 protons and 11 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 20 + 11 = 31.

12 questions · Seed 45 · Age guidance, not curriculum certification