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.

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

   12 electrons
3. 2.

   Using the tally, which particle is oxidized, Jun?

   • The Cu²⁺ ion
   • Neither particle
   • The zinc atom
4. 3.

   Using the tally, where do zinc's two electrons go, Kira?

   Use the picture in question 2.

   • To another zinc atom
   • To the Cu²⁺ ion
   • Off into the air
5. 4.

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

   Use the picture in question 2.

   • Copper metal
   • A Cu⁴⁺ ion
   • Zinc metal
6. 5.

   What is oxidation, Milo?

   • Losing electrons
   • Gaining electrons
   • Gaining protons
7. 6.

   What is reduction, Noah?

   • Gaining electrons
   • Losing some of its mass
   • Losing electrons
8. 7.

   Why do oxidation and reduction happen together, Pia?

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

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

   • −2
   • 0
   • +1
10. 9.

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

    • +2
    • −2
    • 0
11. 10.

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

    • +2
    • −1
    • +1