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 3 neutrons. What is its mass number?
4 p⁺ · 3 n⁰ · A = Z + N = ?
2. An atom has 20 protons and 8 neutrons. What is its mass number?
20 p⁺ · 8 n⁰ · A = Z + N = ?
3. An atom has 13 protons and 16 neutrons. What is its mass number?
13 p⁺ · 16 n⁰ · A = Z + N = ?
4. An atom has 2 protons and 6 neutrons. What is its mass number?
2 p⁺ · 6 n⁰ · A = Z + N = ?
5. An atom has 17 protons and 26 neutrons. What is its mass number?
17 p⁺ · 26 n⁰ · A = Z + N = ?
6. An atom has 1 protons and 3 neutrons. What is its mass number?
1 p⁺ · 3 n⁰ · A = Z + N = ?
7. An atom has 5 protons and 15 neutrons. What is its mass number?
5 p⁺ · 15 n⁰ · A = Z + N = ?
8. An atom has 16 protons and 18 neutrons. What is its mass number?
16 p⁺ · 18 n⁰ · A = Z + N = ?
9. An atom has 10 protons and 17 neutrons. What is its mass number?
10 p⁺ · 17 n⁰ · A = Z + N = ?
10. An atom has 13 protons and 29 neutrons. What is its mass number?
13 p⁺ · 29 n⁰ · A = Z + N = ?
11. An atom has 7 protons and 4 neutrons. What is its mass number?
7 p⁺ · 4 n⁰ · A = Z + N = ?
12. An atom has 12 protons and 6 neutrons. What is its mass number?
12 p⁺ · 6 n⁰ · A = Z + N = ?

12 questions · Seed 51 · 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 3 neutrons. What is its mass number?
7
Mass number counts protons and neutrons: 4 + 3 = 7.
2. An atom has 20 protons and 8 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 20 + 8 = 28.
3. An atom has 13 protons and 16 neutrons. What is its mass number?
29
Mass number counts protons and neutrons: 13 + 16 = 29.
4. An atom has 2 protons and 6 neutrons. What is its mass number?
8
Mass number counts protons and neutrons: 2 + 6 = 8.
5. An atom has 17 protons and 26 neutrons. What is its mass number?
43
Mass number counts protons and neutrons: 17 + 26 = 43.
6. An atom has 1 protons and 3 neutrons. What is its mass number?
4
Mass number counts protons and neutrons: 1 + 3 = 4.
7. An atom has 5 protons and 15 neutrons. What is its mass number?
20
Mass number counts protons and neutrons: 5 + 15 = 20.
8. An atom has 16 protons and 18 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 16 + 18 = 34.
9. An atom has 10 protons and 17 neutrons. What is its mass number?
27
Mass number counts protons and neutrons: 10 + 17 = 27.
10. An atom has 13 protons and 29 neutrons. What is its mass number?
42
Mass number counts protons and neutrons: 13 + 29 = 42.
11. An atom has 7 protons and 4 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 7 + 4 = 11.
12. An atom has 12 protons and 6 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 12 + 6 = 18.

12 questions · Seed 51 · 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 3 neutrons. What is its mass number?
4 p⁺ · 3 n⁰ · A = Z + N = ?
2. An atom has 20 protons and 8 neutrons. What is its mass number?
20 p⁺ · 8 n⁰ · A = Z + N = ?
3. An atom has 13 protons and 16 neutrons. What is its mass number?
13 p⁺ · 16 n⁰ · A = Z + N = ?
4. An atom has 2 protons and 6 neutrons. What is its mass number?
2 p⁺ · 6 n⁰ · A = Z + N = ?
5. An atom has 17 protons and 26 neutrons. What is its mass number?
17 p⁺ · 26 n⁰ · A = Z + N = ?
6. An atom has 1 protons and 3 neutrons. What is its mass number?
1 p⁺ · 3 n⁰ · A = Z + N = ?
7. An atom has 5 protons and 15 neutrons. What is its mass number?
5 p⁺ · 15 n⁰ · A = Z + N = ?
8. An atom has 16 protons and 18 neutrons. What is its mass number?
16 p⁺ · 18 n⁰ · A = Z + N = ?
9. An atom has 10 protons and 17 neutrons. What is its mass number?
10 p⁺ · 17 n⁰ · A = Z + N = ?
10. An atom has 13 protons and 29 neutrons. What is its mass number?
13 p⁺ · 29 n⁰ · A = Z + N = ?
11. An atom has 7 protons and 4 neutrons. What is its mass number?
7 p⁺ · 4 n⁰ · A = Z + N = ?
12. An atom has 12 protons and 6 neutrons. What is its mass number?
12 p⁺ · 6 n⁰ · A = Z + N = ?

12 questions · Seed 51 · 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 3 neutrons. What is its mass number?
7
Mass number counts protons and neutrons: 4 + 3 = 7.
2. An atom has 20 protons and 8 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 20 + 8 = 28.
3. An atom has 13 protons and 16 neutrons. What is its mass number?
29
Mass number counts protons and neutrons: 13 + 16 = 29.
4. An atom has 2 protons and 6 neutrons. What is its mass number?
8
Mass number counts protons and neutrons: 2 + 6 = 8.
5. An atom has 17 protons and 26 neutrons. What is its mass number?
43
Mass number counts protons and neutrons: 17 + 26 = 43.
6. An atom has 1 protons and 3 neutrons. What is its mass number?
4
Mass number counts protons and neutrons: 1 + 3 = 4.
7. An atom has 5 protons and 15 neutrons. What is its mass number?
20
Mass number counts protons and neutrons: 5 + 15 = 20.
8. An atom has 16 protons and 18 neutrons. What is its mass number?
34
Mass number counts protons and neutrons: 16 + 18 = 34.
9. An atom has 10 protons and 17 neutrons. What is its mass number?
27
Mass number counts protons and neutrons: 10 + 17 = 27.
10. An atom has 13 protons and 29 neutrons. What is its mass number?
42
Mass number counts protons and neutrons: 13 + 29 = 42.
11. An atom has 7 protons and 4 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 7 + 4 = 11.
12. An atom has 12 protons and 6 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 12 + 6 = 18.

12 questions · Seed 51 · Age guidance, not curriculum certification