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 2 protons and 7 neutrons. What is its mass number?
2 p⁺ · 7 n⁰ · A = Z + N = ?
2. An atom has 8 protons and 20 neutrons. What is its mass number?
8 p⁺ · 20 n⁰ · A = Z + N = ?
3. An atom has 1 protons and 5 neutrons. What is its mass number?
1 p⁺ · 5 n⁰ · A = Z + N = ?
4. An atom has 1 protons and 8 neutrons. What is its mass number?
1 p⁺ · 8 n⁰ · A = Z + N = ?
5. An atom has 7 protons and 29 neutrons. What is its mass number?
7 p⁺ · 29 n⁰ · A = Z + N = ?
6. An atom has 2 protons and 12 neutrons. What is its mass number?
2 p⁺ · 12 n⁰ · A = Z + N = ?
7. An atom has 20 protons and 4 neutrons. What is its mass number?
20 p⁺ · 4 n⁰ · A = Z + N = ?
8. An atom has 3 protons and 5 neutrons. What is its mass number?
3 p⁺ · 5 n⁰ · A = Z + N = ?
9. An atom has 11 protons and 7 neutrons. What is its mass number?
11 p⁺ · 7 n⁰ · A = Z + N = ?
10. An atom has 6 protons and 27 neutrons. What is its mass number?
6 p⁺ · 27 n⁰ · A = Z + N = ?
11. An atom has 6 protons and 26 neutrons. What is its mass number?
6 p⁺ · 26 n⁰ · A = Z + N = ?
12. An atom has 15 protons and 25 neutrons. What is its mass number?
15 p⁺ · 25 n⁰ · A = Z + N = ?

12 questions · Seed 54 · 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 2 protons and 7 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 2 + 7 = 9.
2. An atom has 8 protons and 20 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 8 + 20 = 28.
3. An atom has 1 protons and 5 neutrons. What is its mass number?
6
Mass number counts protons and neutrons: 1 + 5 = 6.
4. An atom has 1 protons and 8 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 1 + 8 = 9.
5. An atom has 7 protons and 29 neutrons. What is its mass number?
36
Mass number counts protons and neutrons: 7 + 29 = 36.
6. An atom has 2 protons and 12 neutrons. What is its mass number?
14
Mass number counts protons and neutrons: 2 + 12 = 14.
7. An atom has 20 protons and 4 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 20 + 4 = 24.
8. An atom has 3 protons and 5 neutrons. What is its mass number?
8
Mass number counts protons and neutrons: 3 + 5 = 8.
9. An atom has 11 protons and 7 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 11 + 7 = 18.
10. An atom has 6 protons and 27 neutrons. What is its mass number?
33
Mass number counts protons and neutrons: 6 + 27 = 33.
11. An atom has 6 protons and 26 neutrons. What is its mass number?
32
Mass number counts protons and neutrons: 6 + 26 = 32.
12. An atom has 15 protons and 25 neutrons. What is its mass number?
40
Mass number counts protons and neutrons: 15 + 25 = 40.

12 questions · Seed 54 · 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 2 protons and 7 neutrons. What is its mass number?
2 p⁺ · 7 n⁰ · A = Z + N = ?
2. An atom has 8 protons and 20 neutrons. What is its mass number?
8 p⁺ · 20 n⁰ · A = Z + N = ?
3. An atom has 1 protons and 5 neutrons. What is its mass number?
1 p⁺ · 5 n⁰ · A = Z + N = ?
4. An atom has 1 protons and 8 neutrons. What is its mass number?
1 p⁺ · 8 n⁰ · A = Z + N = ?
5. An atom has 7 protons and 29 neutrons. What is its mass number?
7 p⁺ · 29 n⁰ · A = Z + N = ?
6. An atom has 2 protons and 12 neutrons. What is its mass number?
2 p⁺ · 12 n⁰ · A = Z + N = ?
7. An atom has 20 protons and 4 neutrons. What is its mass number?
20 p⁺ · 4 n⁰ · A = Z + N = ?
8. An atom has 3 protons and 5 neutrons. What is its mass number?
3 p⁺ · 5 n⁰ · A = Z + N = ?
9. An atom has 11 protons and 7 neutrons. What is its mass number?
11 p⁺ · 7 n⁰ · A = Z + N = ?
10. An atom has 6 protons and 27 neutrons. What is its mass number?
6 p⁺ · 27 n⁰ · A = Z + N = ?
11. An atom has 6 protons and 26 neutrons. What is its mass number?
6 p⁺ · 26 n⁰ · A = Z + N = ?
12. An atom has 15 protons and 25 neutrons. What is its mass number?
15 p⁺ · 25 n⁰ · A = Z + N = ?

12 questions · Seed 54 · 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 2 protons and 7 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 2 + 7 = 9.
2. An atom has 8 protons and 20 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 8 + 20 = 28.
3. An atom has 1 protons and 5 neutrons. What is its mass number?
6
Mass number counts protons and neutrons: 1 + 5 = 6.
4. An atom has 1 protons and 8 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 1 + 8 = 9.
5. An atom has 7 protons and 29 neutrons. What is its mass number?
36
Mass number counts protons and neutrons: 7 + 29 = 36.
6. An atom has 2 protons and 12 neutrons. What is its mass number?
14
Mass number counts protons and neutrons: 2 + 12 = 14.
7. An atom has 20 protons and 4 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 20 + 4 = 24.
8. An atom has 3 protons and 5 neutrons. What is its mass number?
8
Mass number counts protons and neutrons: 3 + 5 = 8.
9. An atom has 11 protons and 7 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 11 + 7 = 18.
10. An atom has 6 protons and 27 neutrons. What is its mass number?
33
Mass number counts protons and neutrons: 6 + 27 = 33.
11. An atom has 6 protons and 26 neutrons. What is its mass number?
32
Mass number counts protons and neutrons: 6 + 26 = 32.
12. An atom has 15 protons and 25 neutrons. What is its mass number?
40
Mass number counts protons and neutrons: 15 + 25 = 40.

12 questions · Seed 54 · Age guidance, not curriculum certification