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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Age band:Ages 13-15 Ages 16-18

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Worksheet StudioPractice pack · Ages 16-18

Protons, neutrons & mass number

Take your time. Show your thinking.

1. An atom has 16 protons and 15 neutrons. What is its mass number?
16 p⁺ · 15 n⁰ · A = Z + N = ?
2. An atom has 8 protons and 13 neutrons. What is its mass number?
8 p⁺ · 13 n⁰ · A = Z + N = ?
3. An atom has 10 protons and 7 neutrons. What is its mass number?
10 p⁺ · 7 n⁰ · A = Z + N = ?
4. An atom has 6 protons and 9 neutrons. What is its mass number?
6 p⁺ · 9 n⁰ · A = Z + N = ?
5. An atom has 8 protons and 16 neutrons. What is its mass number?
8 p⁺ · 16 n⁰ · A = Z + N = ?
6. An atom has 20 protons and 6 neutrons. What is its mass number?
20 p⁺ · 6 n⁰ · A = Z + N = ?
7. An atom has 12 protons and 4 neutrons. What is its mass number?
12 p⁺ · 4 n⁰ · A = Z + N = ?
8. An atom has 15 protons and 3 neutrons. What is its mass number?
15 p⁺ · 3 n⁰ · A = Z + N = ?
9. An atom has 18 protons and 28 neutrons. What is its mass number?
18 p⁺ · 28 n⁰ · A = Z + N = ?
10. An atom has 11 protons and 29 neutrons. What is its mass number?
11 p⁺ · 29 n⁰ · A = Z + N = ?
11. An atom has 13 protons and 14 neutrons. What is its mass number?
13 p⁺ · 14 n⁰ · A = Z + N = ?
12. An atom has 6 protons and 25 neutrons. What is its mass number?
6 p⁺ · 25 n⁰ · A = Z + N = ?

12 questions · Seed 47 · 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 16 protons and 15 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 16 + 15 = 31.
2. An atom has 8 protons and 13 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 8 + 13 = 21.
3. An atom has 10 protons and 7 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 10 + 7 = 17.
4. An atom has 6 protons and 9 neutrons. What is its mass number?
15
Mass number counts protons and neutrons: 6 + 9 = 15.
5. An atom has 8 protons and 16 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 8 + 16 = 24.
6. An atom has 20 protons and 6 neutrons. What is its mass number?
26
Mass number counts protons and neutrons: 20 + 6 = 26.
7. An atom has 12 protons and 4 neutrons. What is its mass number?
16
Mass number counts protons and neutrons: 12 + 4 = 16.
8. An atom has 15 protons and 3 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 15 + 3 = 18.
9. An atom has 18 protons and 28 neutrons. What is its mass number?
46
Mass number counts protons and neutrons: 18 + 28 = 46.
10. An atom has 11 protons and 29 neutrons. What is its mass number?
40
Mass number counts protons and neutrons: 11 + 29 = 40.
11. An atom has 13 protons and 14 neutrons. What is its mass number?
27
Mass number counts protons and neutrons: 13 + 14 = 27.
12. An atom has 6 protons and 25 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 6 + 25 = 31.

12 questions · Seed 47 · 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 16 protons and 15 neutrons. What is its mass number?
16 p⁺ · 15 n⁰ · A = Z + N = ?
2. An atom has 8 protons and 13 neutrons. What is its mass number?
8 p⁺ · 13 n⁰ · A = Z + N = ?
3. An atom has 10 protons and 7 neutrons. What is its mass number?
10 p⁺ · 7 n⁰ · A = Z + N = ?
4. An atom has 6 protons and 9 neutrons. What is its mass number?
6 p⁺ · 9 n⁰ · A = Z + N = ?
5. An atom has 8 protons and 16 neutrons. What is its mass number?
8 p⁺ · 16 n⁰ · A = Z + N = ?
6. An atom has 20 protons and 6 neutrons. What is its mass number?
20 p⁺ · 6 n⁰ · A = Z + N = ?
7. An atom has 12 protons and 4 neutrons. What is its mass number?
12 p⁺ · 4 n⁰ · A = Z + N = ?
8. An atom has 15 protons and 3 neutrons. What is its mass number?
15 p⁺ · 3 n⁰ · A = Z + N = ?
9. An atom has 18 protons and 28 neutrons. What is its mass number?
18 p⁺ · 28 n⁰ · A = Z + N = ?
10. An atom has 11 protons and 29 neutrons. What is its mass number?
11 p⁺ · 29 n⁰ · A = Z + N = ?
11. An atom has 13 protons and 14 neutrons. What is its mass number?
13 p⁺ · 14 n⁰ · A = Z + N = ?
12. An atom has 6 protons and 25 neutrons. What is its mass number?
6 p⁺ · 25 n⁰ · A = Z + N = ?

12 questions · Seed 47 · 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 16 protons and 15 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 16 + 15 = 31.
2. An atom has 8 protons and 13 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 8 + 13 = 21.
3. An atom has 10 protons and 7 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 10 + 7 = 17.
4. An atom has 6 protons and 9 neutrons. What is its mass number?
15
Mass number counts protons and neutrons: 6 + 9 = 15.
5. An atom has 8 protons and 16 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 8 + 16 = 24.
6. An atom has 20 protons and 6 neutrons. What is its mass number?
26
Mass number counts protons and neutrons: 20 + 6 = 26.
7. An atom has 12 protons and 4 neutrons. What is its mass number?
16
Mass number counts protons and neutrons: 12 + 4 = 16.
8. An atom has 15 protons and 3 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 15 + 3 = 18.
9. An atom has 18 protons and 28 neutrons. What is its mass number?
46
Mass number counts protons and neutrons: 18 + 28 = 46.
10. An atom has 11 protons and 29 neutrons. What is its mass number?
40
Mass number counts protons and neutrons: 11 + 29 = 40.
11. An atom has 13 protons and 14 neutrons. What is its mass number?
27
Mass number counts protons and neutrons: 13 + 14 = 27.
12. An atom has 6 protons and 25 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 6 + 25 = 31.

12 questions · Seed 47 · Age guidance, not curriculum certification