Write formulas for ionic compounds

Answer Key - Grade 10 Science Worksheet - Challenge Me

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

1. 1.

   Al₂O₃ has 3 oxide ions for every 2 aluminum ions. A sample holds 4 aluminum ions. How many oxide ions does it hold, Ari?

   6 ions
2. 2.

   CaCl₂ has 2 chloride ions for every 1 calcium ion. A sample holds 5 calcium ions. How many chloride ions does it hold, Bo?

   10 ions
3. 3.

   Chalk is calcium carbonate. What is its formula, Jun?

   • CaCO₃
   • Ca₂CO₃
   • Ca(CO₃)₂
4. 4.

   In CaCO₃, how is the carbonate part treated, Kira?

   • As a neutral molecule
   • As one ion with a 2− charge
   • As four separate ions
5. 5.

   Why does CaCO₃ have one calcium for each carbonate, Luz?

   • Carbonate has three oxygens
   • +2 and −2 balance
   • Calcium is heavier
6. 6.

   Milo writes magnesium oxide as Mg₂O₂ because each charge is 2. Agree or disagree?

   • Agree: 2 and 2 balance
   • Agree: copy each charge as a count
   • Disagree: reduce it to MgO
7. 7.

   Pia says CaCl₂ has an overall 2+ charge from calcium. Agree or disagree?

   • Disagree: two Cl⁻ cancel it
   • Agree: calcium's charge wins
   • Agree: metals keep their charge
8. 8.

   Which of these formulas is correct, Ren?

   • NaCl₂
   • NaCl
   • Na₂Cl
9. 9.

   Which formula for calcium chloride is correct, Tala?

   • CaCl₂
   • CaCl
   • Ca₂Cl
10. 10.

    Do the charges in MgCl₂ add to zero, Zee?

    • No: it needs three Cl
    • Yes: +2 − 2 = 0
    • No: +2 − 1 = +1