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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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Age band:Ages 13-15Ages 16-18

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Worksheet StudioPractice pack · Ages 13-15

Protons, neutrons & mass number

Take your time. Show your thinking.

  1. 1. An atom has 2 protons and 22 neutrons. What is its mass number?

    2 p⁺ · 22 n⁰ · A = Z + N = ?

  2. 2. An atom has 9 protons and 26 neutrons. What is its mass number?

    9 p⁺ · 26 n⁰ · A = Z + N = ?

  3. 3. An atom has 11 protons and 27 neutrons. What is its mass number?

    11 p⁺ · 27 n⁰ · A = Z + N = ?

  4. 4. An atom has 2 protons and 26 neutrons. What is its mass number?

    2 p⁺ · 26 n⁰ · A = Z + N = ?

  5. 5. An atom has 20 protons and 17 neutrons. What is its mass number?

    20 p⁺ · 17 n⁰ · A = Z + N = ?

  6. 6. An atom has 7 protons and 23 neutrons. What is its mass number?

    7 p⁺ · 23 n⁰ · A = Z + N = ?

  7. 7. An atom has 20 protons and 18 neutrons. What is its mass number?

    20 p⁺ · 18 n⁰ · A = Z + N = ?

  8. 8. An atom has 4 protons and 8 neutrons. What is its mass number?

    4 p⁺ · 8 n⁰ · A = Z + N = ?

  9. 9. An atom has 17 protons and 2 neutrons. What is its mass number?

    17 p⁺ · 2 n⁰ · A = Z + N = ?

  10. 10. An atom has 15 protons and 9 neutrons. What is its mass number?

    15 p⁺ · 9 n⁰ · A = Z + N = ?

  11. 11. An atom has 11 protons and 14 neutrons. What is its mass number?

    11 p⁺ · 14 n⁰ · A = Z + N = ?

  12. 12. An atom has 1 protons and 19 neutrons. What is its mass number?

    1 p⁺ · 19 n⁰ · A = Z + N = ?
12 questions · Seed 48 · 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. 1. An atom has 2 protons and 22 neutrons. What is its mass number?

    24

    Mass number counts protons and neutrons: 2 + 22 = 24.

  2. 2. An atom has 9 protons and 26 neutrons. What is its mass number?

    35

    Mass number counts protons and neutrons: 9 + 26 = 35.

  3. 3. An atom has 11 protons and 27 neutrons. What is its mass number?

    38

    Mass number counts protons and neutrons: 11 + 27 = 38.

  4. 4. An atom has 2 protons and 26 neutrons. What is its mass number?

    28

    Mass number counts protons and neutrons: 2 + 26 = 28.

  5. 5. An atom has 20 protons and 17 neutrons. What is its mass number?

    37

    Mass number counts protons and neutrons: 20 + 17 = 37.

  6. 6. An atom has 7 protons and 23 neutrons. What is its mass number?

    30

    Mass number counts protons and neutrons: 7 + 23 = 30.

  7. 7. An atom has 20 protons and 18 neutrons. What is its mass number?

    38

    Mass number counts protons and neutrons: 20 + 18 = 38.

  8. 8. An atom has 4 protons and 8 neutrons. What is its mass number?

    12

    Mass number counts protons and neutrons: 4 + 8 = 12.

  9. 9. An atom has 17 protons and 2 neutrons. What is its mass number?

    19

    Mass number counts protons and neutrons: 17 + 2 = 19.

  10. 10. An atom has 15 protons and 9 neutrons. What is its mass number?

    24

    Mass number counts protons and neutrons: 15 + 9 = 24.

  11. 11. An atom has 11 protons and 14 neutrons. What is its mass number?

    25

    Mass number counts protons and neutrons: 11 + 14 = 25.

  12. 12. An atom has 1 protons and 19 neutrons. What is its mass number?

    20

    Mass number counts protons and neutrons: 1 + 19 = 20.

12 questions · Seed 48 · Age guidance, not curriculum certification
Worksheet StudioPractice pack · Ages 13-15

Protons, neutrons & mass number

Take your time. Show your thinking.

  1. 1. An atom has 2 protons and 22 neutrons. What is its mass number?

    2 p⁺ · 22 n⁰ · A = Z + N = ?

  2. 2. An atom has 9 protons and 26 neutrons. What is its mass number?

    9 p⁺ · 26 n⁰ · A = Z + N = ?

  3. 3. An atom has 11 protons and 27 neutrons. What is its mass number?

    11 p⁺ · 27 n⁰ · A = Z + N = ?

  4. 4. An atom has 2 protons and 26 neutrons. What is its mass number?

    2 p⁺ · 26 n⁰ · A = Z + N = ?

  5. 5. An atom has 20 protons and 17 neutrons. What is its mass number?

    20 p⁺ · 17 n⁰ · A = Z + N = ?

  6. 6. An atom has 7 protons and 23 neutrons. What is its mass number?

    7 p⁺ · 23 n⁰ · A = Z + N = ?

  7. 7. An atom has 20 protons and 18 neutrons. What is its mass number?

    20 p⁺ · 18 n⁰ · A = Z + N = ?

  8. 8. An atom has 4 protons and 8 neutrons. What is its mass number?

    4 p⁺ · 8 n⁰ · A = Z + N = ?

  9. 9. An atom has 17 protons and 2 neutrons. What is its mass number?

    17 p⁺ · 2 n⁰ · A = Z + N = ?

  10. 10. An atom has 15 protons and 9 neutrons. What is its mass number?

    15 p⁺ · 9 n⁰ · A = Z + N = ?

  11. 11. An atom has 11 protons and 14 neutrons. What is its mass number?

    11 p⁺ · 14 n⁰ · A = Z + N = ?

  12. 12. An atom has 1 protons and 19 neutrons. What is its mass number?

    1 p⁺ · 19 n⁰ · A = Z + N = ?
12 questions · Seed 48 · Age guidance, not curriculum certification
Worksheet StudioAnswer key · Ages 13-15

Protons, neutrons & mass number

Answers and reasoning. Review before teaching.

  1. 1. An atom has 2 protons and 22 neutrons. What is its mass number?

    24

    Mass number counts protons and neutrons: 2 + 22 = 24.

  2. 2. An atom has 9 protons and 26 neutrons. What is its mass number?

    35

    Mass number counts protons and neutrons: 9 + 26 = 35.

  3. 3. An atom has 11 protons and 27 neutrons. What is its mass number?

    38

    Mass number counts protons and neutrons: 11 + 27 = 38.

  4. 4. An atom has 2 protons and 26 neutrons. What is its mass number?

    28

    Mass number counts protons and neutrons: 2 + 26 = 28.

  5. 5. An atom has 20 protons and 17 neutrons. What is its mass number?

    37

    Mass number counts protons and neutrons: 20 + 17 = 37.

  6. 6. An atom has 7 protons and 23 neutrons. What is its mass number?

    30

    Mass number counts protons and neutrons: 7 + 23 = 30.

  7. 7. An atom has 20 protons and 18 neutrons. What is its mass number?

    38

    Mass number counts protons and neutrons: 20 + 18 = 38.

  8. 8. An atom has 4 protons and 8 neutrons. What is its mass number?

    12

    Mass number counts protons and neutrons: 4 + 8 = 12.

  9. 9. An atom has 17 protons and 2 neutrons. What is its mass number?

    19

    Mass number counts protons and neutrons: 17 + 2 = 19.

  10. 10. An atom has 15 protons and 9 neutrons. What is its mass number?

    24

    Mass number counts protons and neutrons: 15 + 9 = 24.

  11. 11. An atom has 11 protons and 14 neutrons. What is its mass number?

    25

    Mass number counts protons and neutrons: 11 + 14 = 25.

  12. 12. An atom has 1 protons and 19 neutrons. What is its mass number?

    20

    Mass number counts protons and neutrons: 1 + 19 = 20.

12 questions · Seed 48 · Age guidance, not curriculum certification