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

12 questions · Seed 104729 · 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 19 protons and 4 neutrons. What is its mass number?
23
Mass number counts protons and neutrons: 19 + 4 = 23.
2. An atom has 1 protons and 8 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 1 + 8 = 9.
3. An atom has 7 protons and 11 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 7 + 11 = 18.
4. An atom has 10 protons and 19 neutrons. What is its mass number?
29
Mass number counts protons and neutrons: 10 + 19 = 29.
5. An atom has 20 protons and 10 neutrons. What is its mass number?
30
Mass number counts protons and neutrons: 20 + 10 = 30.
6. An atom has 20 protons and 19 neutrons. What is its mass number?
39
Mass number counts protons and neutrons: 20 + 19 = 39.
7. An atom has 20 protons and 20 neutrons. What is its mass number?
40
Mass number counts protons and neutrons: 20 + 20 = 40.
8. An atom has 9 protons and 20 neutrons. What is its mass number?
29
Mass number counts protons and neutrons: 9 + 20 = 29.
9. An atom has 9 protons and 8 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 9 + 8 = 17.
10. An atom has 11 protons and 12 neutrons. What is its mass number?
23
Mass number counts protons and neutrons: 11 + 12 = 23.
11. An atom has 12 protons and 7 neutrons. What is its mass number?
19
Mass number counts protons and neutrons: 12 + 7 = 19.
12. An atom has 4 protons and 5 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 4 + 5 = 9.

12 questions · Seed 104729 · 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 19 protons and 4 neutrons. What is its mass number?
19 p⁺ · 4 n⁰ · A = Z + N = ?
2. An atom has 1 protons and 8 neutrons. What is its mass number?
1 p⁺ · 8 n⁰ · A = Z + N = ?
3. An atom has 7 protons and 11 neutrons. What is its mass number?
7 p⁺ · 11 n⁰ · A = Z + N = ?
4. An atom has 10 protons and 19 neutrons. What is its mass number?
10 p⁺ · 19 n⁰ · A = Z + N = ?
5. An atom has 20 protons and 10 neutrons. What is its mass number?
20 p⁺ · 10 n⁰ · A = Z + N = ?
6. An atom has 20 protons and 19 neutrons. What is its mass number?
20 p⁺ · 19 n⁰ · A = Z + N = ?
7. An atom has 20 protons and 20 neutrons. What is its mass number?
20 p⁺ · 20 n⁰ · A = Z + N = ?
8. An atom has 9 protons and 20 neutrons. What is its mass number?
9 p⁺ · 20 n⁰ · A = Z + N = ?
9. An atom has 9 protons and 8 neutrons. What is its mass number?
9 p⁺ · 8 n⁰ · A = Z + N = ?
10. An atom has 11 protons and 12 neutrons. What is its mass number?
11 p⁺ · 12 n⁰ · A = Z + N = ?
11. An atom has 12 protons and 7 neutrons. What is its mass number?
12 p⁺ · 7 n⁰ · A = Z + N = ?
12. An atom has 4 protons and 5 neutrons. What is its mass number?
4 p⁺ · 5 n⁰ · A = Z + N = ?

12 questions · Seed 104729 · 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 19 protons and 4 neutrons. What is its mass number?
23
Mass number counts protons and neutrons: 19 + 4 = 23.
2. An atom has 1 protons and 8 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 1 + 8 = 9.
3. An atom has 7 protons and 11 neutrons. What is its mass number?
18
Mass number counts protons and neutrons: 7 + 11 = 18.
4. An atom has 10 protons and 19 neutrons. What is its mass number?
29
Mass number counts protons and neutrons: 10 + 19 = 29.
5. An atom has 20 protons and 10 neutrons. What is its mass number?
30
Mass number counts protons and neutrons: 20 + 10 = 30.
6. An atom has 20 protons and 19 neutrons. What is its mass number?
39
Mass number counts protons and neutrons: 20 + 19 = 39.
7. An atom has 20 protons and 20 neutrons. What is its mass number?
40
Mass number counts protons and neutrons: 20 + 20 = 40.
8. An atom has 9 protons and 20 neutrons. What is its mass number?
29
Mass number counts protons and neutrons: 9 + 20 = 29.
9. An atom has 9 protons and 8 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 9 + 8 = 17.
10. An atom has 11 protons and 12 neutrons. What is its mass number?
23
Mass number counts protons and neutrons: 11 + 12 = 23.
11. An atom has 12 protons and 7 neutrons. What is its mass number?
19
Mass number counts protons and neutrons: 12 + 7 = 19.
12. An atom has 4 protons and 5 neutrons. What is its mass number?
9
Mass number counts protons and neutrons: 4 + 5 = 9.

12 questions · Seed 104729 · Age guidance, not curriculum certification