Oxidation and reduction: losing and gaining electrons

Answer Key - Grade 10 Science Worksheet - Building Confidence

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

1. 1.

   In a battery, 5 zinc atoms each lose 2 electrons to become Zn²⁺. How many electrons are lost in all, Ari?

   10 electrons
2. 2.

   4 aluminum atoms each lose 3 electrons to become Al³⁺. How many electrons are lost in all, Bo?

   12 electrons
3. 3.

   As a nail rusts, 6 iron atoms each end up losing 3 electrons, becoming iron(III). How many electrons are lost in all, Esme?

   18 electrons
5. 4.

   Using the tally, which particle is oxidized, Jun?

   • Neither particle
   • The Cu²⁺ ion
   • The zinc atom
6. 5.

   Using the tally, what does the Cu²⁺ ion become, Luz?

   Use the picture in question 4.

   • Copper metal
   • Zinc metal
   • A Cu⁴⁺ ion
7. 6.

   What is oxidation, Milo?

   • Gaining protons
   • Gaining electrons
   • Losing electrons
8. 7.

   Why do oxidation and reduction happen together, Pia?

   • Atoms cannot be split into pieces
   • Oxygen must be present
   • Lost electrons must go somewhere
9. 8.

   What is the oxidation number of a pure element, such as Fe or O₂, Ren?

   • +1
   • 0
   • −2
10. 9.

    What oxidation number does oxygen usually have in compounds, Tala?

    • 0
    • +2
    • −2
11. 10.

    What is the oxidation number of sodium in NaCl, Zee?

    • −1
    • +1
    • +2