Protons, neutrons and electrons

Answer Key - Grade 8 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   A sodium atom has atomic number 11 and mass number 23. Neutrons = mass number − atomic number. How many neutrons does it have, Ari?

   12 neutrons
2. 2.

   An aluminum atom has atomic number 13 and mass number 27. Neutrons = mass number − atomic number. How many neutrons does it have, Bo?

   14 neutrons
3. 3.

   A fluorine atom has atomic number 9 and mass number 19. Neutrons = mass number − atomic number. How many neutrons does it have, Esme?

   10 neutrons
4. 4.

   Jun fills in a particle table. Which particle has a negative charge?

   • The electron
   • The proton
   • The neutron
5. 5.

   Where in an atom are the protons, Kira?

   • In the nucleus
   • Spread through the whole atom
   • Circling outside the nucleus
6. 6.

   Luz asks which particle in an atom has no charge. Which one?

   • The neutron
   • The proton
   • No such particle; each has a charge
8. 7.

   Milo labels a drawing of a helium atom. Which letter marks an electron?

   • Letter A, since electrons sit in the nucleus
   • Letter C
   • Letter B
9. 8.

   In the same helium drawing, what is particle B, Noah?

   Use the picture in question 7.

   • A neutron
   • An electron inside the nucleus
   • A proton
10. 9.

    A neutral carbon atom has 6 protons and 6 neutrons. How many electrons does it have, Ren?

    • 6 electrons
    • 0 electrons, since they are tiny
    • 12 electrons, the mass number
11. 10.

    A neutral sodium atom has atomic number 11 and mass number 23. How many electrons, Zee?

    • 23 electrons
    • 12 electrons
    • 11 electrons