Predict a simple reaction from the outer electrons

Answer Key - Grade 10 Science Worksheet - Building Confidence

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

1. 1.

   Nitrogen is in group 15. How many electrons does one nitrogen atom gain to reach eight outer electrons, Bo?

   3 electron(s)
2. 2.

   Chlorine is in group 17. How many electrons does one chlorine atom gain to reach eight outer electrons, Esme?

   1 electron(s)
3. 3.

   Aluminum is in group 13. Which ion is it predicted to form, Jun?

   • Al³⁻, after gaining 3 electrons
   • Al³⁺, after losing its 3 outer electrons
   • Al¹³⁺, copying the group number
4. 4.

   Sulfur is in group 16. Which ion is it predicted to form, Kira?

   • S²⁺, after losing 2 electrons from its outer shell
   • S⁶⁻, gaining its 6 outer electrons again
   • S²⁻, after gaining 2 electrons to reach eight
5. 5.

   Barium is in group 2 and iodine is in group 17. Which pair of ions is predicted, Luz?

   • Ba²⁻ and I⁺, since the metal gains and the nonmetal loses
   • Ba²⁺ and I⁻, since barium loses 2 and iodine gains 1
   • Ba²⁺ and I⁷⁻, since iodine gains its 7 outer electrons
6. 6.

   Lithium and potassium each have 1 outer electron. Which reacts more vigorously with water, and why, Milo?

   • Potassium: its outer electron is farther from the nucleus, so it is lost more easily
   • Lithium: its smaller atom holds its outer electron more loosely
   • Neither: the same number of outer electrons means the same reactivity
7. 7.

   Fluorine and iodine each gain 1 electron. Which pulls in an electron more strongly, Noah?

   • Both pull equally, since each needs exactly 1 electron
   • Fluorine: its outer shell is closest to the nucleus, so the pull is strongest
   • Iodine: it has more electrons, so it pulls a new one in harder
8. 8.

   Potassium (group 1) combines with sulfur (group 16). Which formula is predicted, Ren?

   • KS, because one of each pairs them
   • KS₂, because the subscripts swap places
   • K₂S, because two K⁺ cancel one S²⁻
9. 9.

   Calcium (group 2) combines with chlorine (group 17). Which formula is predicted, Tala?

   • CaCl, because one of each pairs them
   • CaCl₂, because one Ca²⁺ needs two Cl⁻
   • Ca₂Cl, because the subscripts swap places
10. 10.

    Lithium (group 1) combines with oxygen (group 16). Which formula is predicted, Zee?

    • Li₂O, because two Li⁺ cancel one O²⁻
    • LiO, because one of each pairs them
    • LiO₂, because the subscripts swap places