ScienceAges 13-15

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 13-15

Protons, neutrons & mass number

Take your time. Show your thinking.

1. An atom has 4 protons and 14 neutrons. What is its mass number?
4 p⁺ · 14 n⁰ · A = Z + N = ?
2. An atom has 19 protons and 2 neutrons. What is its mass number?
19 p⁺ · 2 n⁰ · A = Z + N = ?
3. An atom has 14 protons and 17 neutrons. What is its mass number?
14 p⁺ · 17 n⁰ · A = Z + N = ?
4. An atom has 5 protons and 7 neutrons. What is its mass number?
5 p⁺ · 7 n⁰ · A = Z + N = ?
5. An atom has 8 protons and 27 neutrons. What is its mass number?
8 p⁺ · 27 n⁰ · A = Z + N = ?
6. An atom has 10 protons and 11 neutrons. What is its mass number?
10 p⁺ · 11 n⁰ · A = Z + N = ?
7. An atom has 9 protons and 25 neutrons. What is its mass number?
9 p⁺ · 25 n⁰ · A = Z + N = ?
8. An atom has 18 protons and 16 neutrons. What is its mass number?
18 p⁺ · 16 n⁰ · A = Z + N = ?
9. An atom has 15 protons and 4 neutrons. What is its mass number?
15 p⁺ · 4 n⁰ · A = Z + N = ?
10. An atom has 20 protons and 2 neutrons. What is its mass number?
20 p⁺ · 2 n⁰ · A = Z + N = ?
11. An atom has 5 protons and 6 neutrons. What is its mass number?
5 p⁺ · 6 n⁰ · A = Z + N = ?
12. An atom has 20 protons and 14 neutrons. What is its mass number?
20 p⁺ · 14 n⁰ · A = Z + N = ?

12 questions · Seed 46 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 13-15

Protons, neutrons & mass number

Answers and reasoning. Review before teaching.

1. An atom has 4 protons and 14 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 4 + 14 = 18.
2. An atom has 19 protons and 2 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 19 + 2 = 21.
3. An atom has 14 protons and 17 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 14 + 17 = 31.
4. An atom has 5 protons and 7 neutrons. What is its mass number?
12
Mass number counts protons and neutrons: 5 + 7 = 12.
5. An atom has 8 protons and 27 neutrons. What is its mass number?
35
Mass number counts protons and neutrons: 8 + 27 = 35.
6. An atom has 10 protons and 11 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 10 + 11 = 21.
7. An atom has 9 protons and 25 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 9 + 25 = 34.
8. An atom has 18 protons and 16 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 18 + 16 = 34.
9. An atom has 15 protons and 4 neutrons. What is its mass number?
19
Mass number counts protons and neutrons: 15 + 4 = 19.
10. An atom has 20 protons and 2 neutrons. What is its mass number?
22
Mass number counts protons and neutrons: 20 + 2 = 22.
11. An atom has 5 protons and 6 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 5 + 6 = 11.
12. An atom has 20 protons and 14 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 20 + 14 = 34.

12 questions · Seed 46 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Protons, neutrons & mass number

Take your time. Show your thinking.

1. An atom has 4 protons and 14 neutrons. What is its mass number?
4 p⁺ · 14 n⁰ · A = Z + N = ?
2. An atom has 19 protons and 2 neutrons. What is its mass number?
19 p⁺ · 2 n⁰ · A = Z + N = ?
3. An atom has 14 protons and 17 neutrons. What is its mass number?
14 p⁺ · 17 n⁰ · A = Z + N = ?
4. An atom has 5 protons and 7 neutrons. What is its mass number?
5 p⁺ · 7 n⁰ · A = Z + N = ?
5. An atom has 8 protons and 27 neutrons. What is its mass number?
8 p⁺ · 27 n⁰ · A = Z + N = ?
6. An atom has 10 protons and 11 neutrons. What is its mass number?
10 p⁺ · 11 n⁰ · A = Z + N = ?
7. An atom has 9 protons and 25 neutrons. What is its mass number?
9 p⁺ · 25 n⁰ · A = Z + N = ?
8. An atom has 18 protons and 16 neutrons. What is its mass number?
18 p⁺ · 16 n⁰ · A = Z + N = ?
9. An atom has 15 protons and 4 neutrons. What is its mass number?
15 p⁺ · 4 n⁰ · A = Z + N = ?
10. An atom has 20 protons and 2 neutrons. What is its mass number?
20 p⁺ · 2 n⁰ · A = Z + N = ?
11. An atom has 5 protons and 6 neutrons. What is its mass number?
5 p⁺ · 6 n⁰ · A = Z + N = ?
12. An atom has 20 protons and 14 neutrons. What is its mass number?
20 p⁺ · 14 n⁰ · A = Z + N = ?

12 questions · Seed 46 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Protons, neutrons & mass number

Answers and reasoning. Review before teaching.

1. An atom has 4 protons and 14 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 4 + 14 = 18.
2. An atom has 19 protons and 2 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 19 + 2 = 21.
3. An atom has 14 protons and 17 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 14 + 17 = 31.
4. An atom has 5 protons and 7 neutrons. What is its mass number?
12
Mass number counts protons and neutrons: 5 + 7 = 12.
5. An atom has 8 protons and 27 neutrons. What is its mass number?
35
Mass number counts protons and neutrons: 8 + 27 = 35.
6. An atom has 10 protons and 11 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 10 + 11 = 21.
7. An atom has 9 protons and 25 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 9 + 25 = 34.
8. An atom has 18 protons and 16 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 18 + 16 = 34.
9. An atom has 15 protons and 4 neutrons. What is its mass number?
19
Mass number counts protons and neutrons: 15 + 4 = 19.
10. An atom has 20 protons and 2 neutrons. What is its mass number?
22
Mass number counts protons and neutrons: 20 + 2 = 22.
11. An atom has 5 protons and 6 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 5 + 6 = 11.
12. An atom has 20 protons and 14 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 20 + 14 = 34.

12 questions · Seed 46 · Age guidance, not curriculum certification