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 1 protons and 3 neutrons. What is its mass number?
1 p⁺ · 3 n⁰ · A = Z + N = ?
2. An atom has 3 protons and 8 neutrons. What is its mass number?
3 p⁺ · 8 n⁰ · A = Z + N = ?
3. An atom has 5 protons and 15 neutrons. What is its mass number?
5 p⁺ · 15 n⁰ · A = Z + N = ?
4. An atom has 7 protons and 4 neutrons. What is its mass number?
7 p⁺ · 4 n⁰ · A = Z + N = ?
5. An atom has 14 protons and 29 neutrons. What is its mass number?
14 p⁺ · 29 n⁰ · A = Z + N = ?
6. An atom has 12 protons and 21 neutrons. What is its mass number?
12 p⁺ · 21 n⁰ · A = Z + N = ?
7. An atom has 8 protons and 10 neutrons. What is its mass number?
8 p⁺ · 10 n⁰ · A = Z + N = ?
8. An atom has 8 protons and 12 neutrons. What is its mass number?
8 p⁺ · 12 n⁰ · A = Z + N = ?
9. An atom has 12 protons and 6 neutrons. What is its mass number?
12 p⁺ · 6 n⁰ · A = Z + N = ?
10. An atom has 13 protons and 12 neutrons. What is its mass number?
13 p⁺ · 12 n⁰ · A = Z + N = ?
11. An atom has 4 protons and 7 neutrons. What is its mass number?
4 p⁺ · 7 n⁰ · A = Z + N = ?
12. An atom has 13 protons and 4 neutrons. What is its mass number?
13 p⁺ · 4 n⁰ · A = Z + N = ?

12 questions · Seed 56 · 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 1 protons and 3 neutrons. What is its mass number?
4
Mass number counts protons and neutrons: 1 + 3 = 4.
2. An atom has 3 protons and 8 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 3 + 8 = 11.
3. An atom has 5 protons and 15 neutrons. What is its mass number?
20
Mass number counts protons and neutrons: 5 + 15 = 20.
4. An atom has 7 protons and 4 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 7 + 4 = 11.
5. An atom has 14 protons and 29 neutrons. What is its mass number?
43
Mass number counts protons and neutrons: 14 + 29 = 43.
6. An atom has 12 protons and 21 neutrons. What is its mass number?
33
Mass number counts protons and neutrons: 12 + 21 = 33.
7. An atom has 8 protons and 10 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 8 + 10 = 18.
8. An atom has 8 protons and 12 neutrons. What is its mass number?
20
Mass number counts protons and neutrons: 8 + 12 = 20.
9. An atom has 12 protons and 6 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 12 + 6 = 18.
10. An atom has 13 protons and 12 neutrons. What is its mass number?
25
Mass number counts protons and neutrons: 13 + 12 = 25.
11. An atom has 4 protons and 7 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 4 + 7 = 11.
12. An atom has 13 protons and 4 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 13 + 4 = 17.

12 questions · Seed 56 · 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 1 protons and 3 neutrons. What is its mass number?
1 p⁺ · 3 n⁰ · A = Z + N = ?
2. An atom has 3 protons and 8 neutrons. What is its mass number?
3 p⁺ · 8 n⁰ · A = Z + N = ?
3. An atom has 5 protons and 15 neutrons. What is its mass number?
5 p⁺ · 15 n⁰ · A = Z + N = ?
4. An atom has 7 protons and 4 neutrons. What is its mass number?
7 p⁺ · 4 n⁰ · A = Z + N = ?
5. An atom has 14 protons and 29 neutrons. What is its mass number?
14 p⁺ · 29 n⁰ · A = Z + N = ?
6. An atom has 12 protons and 21 neutrons. What is its mass number?
12 p⁺ · 21 n⁰ · A = Z + N = ?
7. An atom has 8 protons and 10 neutrons. What is its mass number?
8 p⁺ · 10 n⁰ · A = Z + N = ?
8. An atom has 8 protons and 12 neutrons. What is its mass number?
8 p⁺ · 12 n⁰ · A = Z + N = ?
9. An atom has 12 protons and 6 neutrons. What is its mass number?
12 p⁺ · 6 n⁰ · A = Z + N = ?
10. An atom has 13 protons and 12 neutrons. What is its mass number?
13 p⁺ · 12 n⁰ · A = Z + N = ?
11. An atom has 4 protons and 7 neutrons. What is its mass number?
4 p⁺ · 7 n⁰ · A = Z + N = ?
12. An atom has 13 protons and 4 neutrons. What is its mass number?
13 p⁺ · 4 n⁰ · A = Z + N = ?

12 questions · Seed 56 · 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 1 protons and 3 neutrons. What is its mass number?
4
Mass number counts protons and neutrons: 1 + 3 = 4.
2. An atom has 3 protons and 8 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 3 + 8 = 11.
3. An atom has 5 protons and 15 neutrons. What is its mass number?
20
Mass number counts protons and neutrons: 5 + 15 = 20.
4. An atom has 7 protons and 4 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 7 + 4 = 11.
5. An atom has 14 protons and 29 neutrons. What is its mass number?
43
Mass number counts protons and neutrons: 14 + 29 = 43.
6. An atom has 12 protons and 21 neutrons. What is its mass number?
33
Mass number counts protons and neutrons: 12 + 21 = 33.
7. An atom has 8 protons and 10 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 8 + 10 = 18.
8. An atom has 8 protons and 12 neutrons. What is its mass number?
20
Mass number counts protons and neutrons: 8 + 12 = 20.
9. An atom has 12 protons and 6 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 12 + 6 = 18.
10. An atom has 13 protons and 12 neutrons. What is its mass number?
25
Mass number counts protons and neutrons: 13 + 12 = 25.
11. An atom has 4 protons and 7 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 4 + 7 = 11.
12. An atom has 13 protons and 4 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 13 + 4 = 17.

12 questions · Seed 56 · Age guidance, not curriculum certification