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

Grade 10 Science Worksheet

NameDate

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

  1. A calcium ion has 20 protons and a 2+ charge. How many electrons does it have, Ari?

  2. A chloride ion has 17 protons and a 1− charge. How many electrons does it have, Bo?

  3. An aluminum ion has 13 protons and a 3+ charge. How many electrons does it have, Esme?

  4. Read this first

    Atom diagram of a fluoride ion

    9 protons and 10 neutrons in the nucleus, and 10 electrons in shells of 2 and 8. Notation: mass number 19 over atomic number 9, then F with a 1− charge.

  5. In the diagram, why is the fluoride ion's charge 1−, Jun?

    • It lost a proton
    • It has one more neutron than protons
    • It has one more electron than protons
  6. In the diagram, why is this still fluorine, Luz?

    • It has 10 electrons in it
    • It gained a proton
    • It still has 9 protons
  7. A sodium atom loses one electron. What does it become, Milo?

    • A 1− ion
    • A 1+ ion
    • A new element
  8. An oxygen atom gains two electrons. What is its charge, Noah?

    • 2−
    • No charge
    • 2+
  9. When an atom becomes an ion, which particles change in number, Pia?

    • Protons
    • Neutrons
    • Electrons
  10. How do carbon-12 and carbon-14 differ, Ren?

    • Carbon-14 has 2 more electrons
    • Carbon-14 has 2 more protons
    • Carbon-14 has 2 more neutrons
  11. How many neutrons does chlorine-37 (atomic number 17) have, Zee?

    • 17
    • 37
    • 20
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Count protons, neutrons and electrons in atoms, ions and isotopes

Answer Key - Grade 10 Science Worksheet

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

  1. A calcium ion has 20 protons and a 2+ charge. How many electrons does it have, Ari?

    18 electrons
  2. A chloride ion has 17 protons and a 1− charge. How many electrons does it have, Bo?

    18 electrons
  3. An aluminum ion has 13 protons and a 3+ charge. How many electrons does it have, Esme?

    10 electrons
  4. Read this first

    Atom diagram of a fluoride ion

    9 protons and 10 neutrons in the nucleus, and 10 electrons in shells of 2 and 8. Notation: mass number 19 over atomic number 9, then F with a 1− charge.

  5. In the diagram, why is the fluoride ion's charge 1−, Jun?

    • It lost a proton
    • It has one more neutron than protons
    • It has one more electron than protons
  6. In the diagram, why is this still fluorine, Luz?

    • It has 10 electrons in it
    • It gained a proton
    • It still has 9 protons
  7. A sodium atom loses one electron. What does it become, Milo?

    • A 1− ion
    • A 1+ ion
    • A new element
  8. An oxygen atom gains two electrons. What is its charge, Noah?

    • 2−
    • No charge
    • 2+
  9. When an atom becomes an ion, which particles change in number, Pia?

    • Protons
    • Neutrons
    • Electrons
  10. How do carbon-12 and carbon-14 differ, Ren?

    • Carbon-14 has 2 more electrons
    • Carbon-14 has 2 more protons
    • Carbon-14 has 2 more neutrons
  11. How many neutrons does chlorine-37 (atomic number 17) have, Zee?

    • 17
    • 37
    • 20