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.

   Sulfur is in group 16. How many electrons does one sulfur atom gain to reach eight outer electrons, Ari?

   2 electron(s)
2. 2.

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

   3 electron(s)
3. 3.

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

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

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

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

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

   • Ba²⁺ and I⁻, since barium loses 2 and iodine gains 1
   • Ba²⁻ and I⁺, since the metal gains and the nonmetal loses
   • 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?

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

   Sodium reacts with chlorine in a 1 to 1 pattern. Which other element should react with chlorine the same way, Pia?

   • Aluminum, the next metal along the same row
   • Magnesium, which sits right beside sodium in the same row
   • Potassium, which also has 1 outer electron
9. 9.

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

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

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

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