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 9 neutrons. What is its mass number?
19 p⁺ · 9 n⁰ · A = Z + N = ?
2. An atom has 6 protons and 5 neutrons. What is its mass number?
6 p⁺ · 5 n⁰ · A = Z + N = ?
3. An atom has 5 protons and 19 neutrons. What is its mass number?
5 p⁺ · 19 n⁰ · A = Z + N = ?
4. An atom has 19 protons and 2 neutrons. What is its mass number?
19 p⁺ · 2 n⁰ · A = Z + N = ?
5. An atom has 11 protons and 26 neutrons. What is its mass number?
11 p⁺ · 26 n⁰ · A = Z + N = ?
6. An atom has 12 protons and 4 neutrons. What is its mass number?
12 p⁺ · 4 n⁰ · A = Z + N = ?
7. An atom has 13 protons and 18 neutrons. What is its mass number?
13 p⁺ · 18 n⁰ · A = Z + N = ?
8. An atom has 12 protons and 13 neutrons. What is its mass number?
12 p⁺ · 13 n⁰ · A = Z + N = ?
9. An atom has 10 protons and 7 neutrons. What is its mass number?
10 p⁺ · 7 n⁰ · A = Z + N = ?
10. An atom has 14 protons and 16 neutrons. What is its mass number?
14 p⁺ · 16 n⁰ · A = Z + N = ?
11. An atom has 19 protons and 30 neutrons. What is its mass number?
19 p⁺ · 30 n⁰ · A = Z + N = ?
12. An atom has 17 protons and 14 neutrons. What is its mass number?
17 p⁺ · 14 n⁰ · A = Z + N = ?

12 questions · Seed 104731 · 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 9 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 19 + 9 = 28.
2. An atom has 6 protons and 5 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 6 + 5 = 11.
3. An atom has 5 protons and 19 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 5 + 19 = 24.
4. An atom has 19 protons and 2 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 19 + 2 = 21.
5. An atom has 11 protons and 26 neutrons. What is its mass number?
37
Mass number counts protons and neutrons: 11 + 26 = 37.
6. An atom has 12 protons and 4 neutrons. What is its mass number?
16
Mass number counts protons and neutrons: 12 + 4 = 16.
7. An atom has 13 protons and 18 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 13 + 18 = 31.
8. An atom has 12 protons and 13 neutrons. What is its mass number?
25
Mass number counts protons and neutrons: 12 + 13 = 25.
9. An atom has 10 protons and 7 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 10 + 7 = 17.
10. An atom has 14 protons and 16 neutrons. What is its mass number?
30
Mass number counts protons and neutrons: 14 + 16 = 30.
11. An atom has 19 protons and 30 neutrons. What is its mass number?
49
Mass number counts protons and neutrons: 19 + 30 = 49.
12. An atom has 17 protons and 14 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 17 + 14 = 31.

12 questions · Seed 104731 · 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 9 neutrons. What is its mass number?
19 p⁺ · 9 n⁰ · A = Z + N = ?
2. An atom has 6 protons and 5 neutrons. What is its mass number?
6 p⁺ · 5 n⁰ · A = Z + N = ?
3. An atom has 5 protons and 19 neutrons. What is its mass number?
5 p⁺ · 19 n⁰ · A = Z + N = ?
4. An atom has 19 protons and 2 neutrons. What is its mass number?
19 p⁺ · 2 n⁰ · A = Z + N = ?
5. An atom has 11 protons and 26 neutrons. What is its mass number?
11 p⁺ · 26 n⁰ · A = Z + N = ?
6. An atom has 12 protons and 4 neutrons. What is its mass number?
12 p⁺ · 4 n⁰ · A = Z + N = ?
7. An atom has 13 protons and 18 neutrons. What is its mass number?
13 p⁺ · 18 n⁰ · A = Z + N = ?
8. An atom has 12 protons and 13 neutrons. What is its mass number?
12 p⁺ · 13 n⁰ · A = Z + N = ?
9. An atom has 10 protons and 7 neutrons. What is its mass number?
10 p⁺ · 7 n⁰ · A = Z + N = ?
10. An atom has 14 protons and 16 neutrons. What is its mass number?
14 p⁺ · 16 n⁰ · A = Z + N = ?
11. An atom has 19 protons and 30 neutrons. What is its mass number?
19 p⁺ · 30 n⁰ · A = Z + N = ?
12. An atom has 17 protons and 14 neutrons. What is its mass number?
17 p⁺ · 14 n⁰ · A = Z + N = ?

12 questions · Seed 104731 · 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 9 neutrons. What is its mass number?
28
Mass number counts protons and neutrons: 19 + 9 = 28.
2. An atom has 6 protons and 5 neutrons. What is its mass number?
11
Mass number counts protons and neutrons: 6 + 5 = 11.
3. An atom has 5 protons and 19 neutrons. What is its mass number?
24
Mass number counts protons and neutrons: 5 + 19 = 24.
4. An atom has 19 protons and 2 neutrons. What is its mass number?
21
Mass number counts protons and neutrons: 19 + 2 = 21.
5. An atom has 11 protons and 26 neutrons. What is its mass number?
37
Mass number counts protons and neutrons: 11 + 26 = 37.
6. An atom has 12 protons and 4 neutrons. What is its mass number?
16
Mass number counts protons and neutrons: 12 + 4 = 16.
7. An atom has 13 protons and 18 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 13 + 18 = 31.
8. An atom has 12 protons and 13 neutrons. What is its mass number?
25
Mass number counts protons and neutrons: 12 + 13 = 25.
9. An atom has 10 protons and 7 neutrons. What is its mass number?
17
Mass number counts protons and neutrons: 10 + 7 = 17.
10. An atom has 14 protons and 16 neutrons. What is its mass number?
30
Mass number counts protons and neutrons: 14 + 16 = 30.
11. An atom has 19 protons and 30 neutrons. What is its mass number?
49
Mass number counts protons and neutrons: 19 + 30 = 49.
12. An atom has 17 protons and 14 neutrons. What is its mass number?
31
Mass number counts protons and neutrons: 17 + 14 = 31.

12 questions · Seed 104731 · Age guidance, not curriculum certification