Count protons, neutrons and electrons in atoms, ions and isotopes

Answer Key - Grade 10 Science Worksheet - Challenge Me

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

1. 1.

   An ion has 12 protons, 12 neutrons and 10 electrons. What is its mass number, Ari?

   24
2. 2.

   An ion has 26 protons, 30 neutrons and 23 electrons. What is its mass number, Esme?

   56
3. 3.

   A particle has 17 protons, 20 neutrons and 18 electrons. How is it written, Jun?

   • Argon-37, neutral
   • Chlorine-37 with a 1− charge
   • Chlorine-37 with a 1+ charge
4. 4.

   A particle has 26 protons, 30 neutrons and 23 electrons. How is it written, Kira?

   • Iron-56 with a 3− charge
   • Iron-79, neutral
   • Iron-56 with a 3+ charge
5. 5.

   A particle has 12 protons, 13 neutrons and 12 electrons. How is it written, Luz?

   • Magnesium-37, neutral
   • Magnesium-25, neutral
   • Sodium-25 with a 1+ charge
6. 6.

   Milo says a sodium ion is no longer sodium because it lost an electron. Agree or disagree?

   • Agree: its proton left with the electron
   • Agree: losing a particle changes the element
   • Disagree: it still has 11 protons
7. 7.

   Pia says carbon-12 and carbon-14 are different elements. Agree or disagree?

   • Disagree: both have 6 protons
   • Agree: the numbers differ
   • Agree: their masses differ
8. 8.

   Na⁺ and F⁻ both have 10 electrons. Are they the same element, Ren?

   • Yes: same electrons, same element
   • Yes, once they are both neutral
   • No: they have different protons
9. 9.

   Argon-40 and calcium-40 have the same mass number. What differs, Tala?

   • Nothing differs between them
   • Their numbers of protons
   • The color of their electrons
10. 10.

    A neutral atom has 15 protons. How many electrons does it have, Zee?

    • 16
    • 15
    • 30