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Grade 12 Atomic Structure & Isotopes Worksheet with Answers

Grade 12 (US) · Year 13 (UK) · Class 12 (India) · Chemistry

Unit 1: Structure of MatterAtoms & ElectronsNGSS HS-PS1-1

Finding protons, neutrons and electrons from atomic number, mass number and charge. This free high school worksheet has 16 questions and a full answer key. Print it or save it as a PDF — every answer is checked by code, not guessed.

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Atomic Structure & Isotopes

Grade 12 · Chemistry

Score___ / 16

Name

Class

Date

Learning goal: Atoms & Electrons · NGSS HS-PS1-1

Directions: This worksheet has 2 parts. Read the instructions at the start of each part.

Example

How many electrons does a neutral atom of beryllium (atomic number 4) have?

Answer: 4

Part A

Label the diagram. Use the words in the box.

Word bank

protonnucleusneutronelectron
+++−−−−−−−−1234
  1. 1
  2. 2
  3. 3
  4. 4
Part B

Answer each question. Use full sentences where you can.

  1. 5

    Lithium-7 has atomic number 3. How many neutrons does it have?

  2. 6

    An isotope of silicon (atomic number 14) has a mass number of 30. How many protons and neutrons does it have?

  3. 7

    How many protons does an atom of aluminum (Al, atomic number 13) have?

  4. 8

    How many protons does an atom of oxygen (O, atomic number 8) have?

  5. 9

    Chlorine-35 has atomic number 17. How many neutrons does it have?

  6. 10

    How many protons does an atom of calcium (Ca, atomic number 20) have?

  7. 11

    An isotope of sulfur (atomic number 16) has a mass number of 35. How many protons and neutrons does it have?

  8. 12

    An isotope of argon (atomic number 18) has a mass number of 42. How many protons and neutrons does it have?

  9. 13

    An isotope of boron (atomic number 5) has a mass number of 12. How many protons and neutrons does it have?

  10. 14

    How many protons does an atom of argon (Ar, atomic number 18) have?

  11. 15

    Phosphorus-31 has atomic number 15. How many neutrons does it have?

  12. 16

    An isotope of sodium (atomic number 11) has a mass number of 26. How many protons and neutrons does it have?

★ Challenge corner for fast finishers

Ice floats in water. What does that tell you about its density?

How did I do?

Teacher's comments

Free printable worksheets with answer keys · aethelsystems.com/worksheets/chemistry/12/atomic_structure

Answer key (click to show)
  1. 1.nucleus
  2. 2.proton
  3. 3.neutron
  4. 4.electron
  5. 5.4
  6. 6.14 protons, 16 neutrons
  7. 7.13
  8. 8.8
  9. 9.18
  10. 10.20
  11. 11.16 protons, 19 neutrons
  12. 12.18 protons, 24 neutrons
  13. 13.5 protons, 7 neutrons
  14. 14.18
  15. 15.16
  16. 16.11 protons, 15 neutrons
  17. ★ice is less dense than liquid water (challenge corner)

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