Write formulas for ionic compounds
Grade 10 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
A sample holds 6 calcium ions, each +2. How many chloride ions, each −1, balance them, Ari?
A sample holds 15 magnesium ions, each +2. How many chloride ions, each −1, balance them, Bo?
A sample holds 4 aluminum ions, each +3. How many oxide ions, each −2, balance them, Esme?
Read this first
Dot diagram
Ions with charges that must add to zero. A calcium atom gives one electron to each of two chlorine atoms. That makes one Ca²⁺ and two Cl⁻: +2 − 1 − 1 = 0, so the formula is CaCl₂.
On the card, how many electrons does calcium give away, Jun?
- 2
- 3
- 1
On the card, why does CaCl₂ need two chloride ions, Kira?
- Calcium has two shells
- Two 1− charges balance one 2+
- Chlorine atoms come in pairs
What charge does an oxide ion (group 16) have, Noah?
- +2
- −6
- −2
What charge does an aluminum ion (group 13) have, Pia?
- +13
- −3
- +3
What must the charges in an ionic formula add up to, Ren?
- One
- Zero
- The cation's charge
Why is table salt's formula NaCl and not NaCl₂, Tala?
- +1 and −1 already add to zero
- Chlorine is lighter than sodium
- Sodium needs two chlorines
Do the charges in MgO add to zero, Zee?
- Yes: +2 − 2 = 0
- No: it needs two O
- No: +2 + 2 = 4