It looks like you've uploaded a
"Chemical Formula Worksheet" with a table of ionic compounds, their cations and anions, and the corresponding chemical formulas. The worksheet is already completed with answers — it appears to be a
teacher's answer key, as indicated by the header "TEACHER'S ANSWER."
Let me explain how to solve this type of problem and verify the answers provided.
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🔍 Objective of the Worksheet
The goal is to
write the correct chemical formula for each ionic compound based on:
- The
cation (positive ion) and
anion (negative ion) given.
- Their respective
charges.
- Using the
criss-cross method or charge balancing to ensure the overall compound is neutral (net charge = 0).
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✔ Steps to Solve Each Problem
1.
Identify the charges of the cation and anion.
2.
Balance the charges so that the total positive charge equals the total negative charge.
3. Use subscripts to show the number of each ion needed.
4.
Simplify subscripts if possible (e.g., 2:4 becomes 1:2).
5. Write the formula with
cation first, then anion.
6.
No subscript of 1 is written.
7. For polyatomic ions, use
parentheses if more than one is needed.
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🧪 Example Walkthrough
Let’s take one example from the table:
####
Lithium chloride
- Cation: Li⁺
- Anion: Cl⁻
- Charges are equal and opposite → 1:1 ratio
- Formula:
LiCl
####
Sodium nitrate
- Na⁺ and NO₃⁻
- Both have 1+ and 1– → 1:1
- Formula:
NaNO₃
####
Calcium sulfate
- Ca²⁺ and SO₄²⁻
- Charges balance at 1:1
- Formula:
CaSO₄
####
Aluminum sulfate
- Al³⁺ and SO₄²⁻
- Need to balance: 2×(Al³⁺) = 6+, 3×(SO₄²⁻) = 6–
- So, Al₂(SO₄)₃
- Note: Parentheses around SO₄ because there are 3 sulfate ions.
✔ All answers in the table follow these rules.
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🔎 Verification of Some Key Entries
| Compound | Cation | Anion | Expected Formula | Given Answer | Correct? |
|--------|--------|-------|------------------|---------------|---------|
| Aluminum sulfate | Al³⁺ | SO₄²⁻ | Al₂(SO₄)₃ | Al₂(SO₄)₃ |
✔ |
| Iron (III) chloride | Fe³⁺ | Cl⁻ | FeCl₃ | FeCl₃ |
✔ |
| Copper (II) chloride | Cu²⁺ | Cl⁻ | CuCl₂ | CuCl₂ |
✔ |
| Magnesium (II) oxide | Mg²⁺ | O²⁻ | MgO | MgO |
✔ |
| Zinc nitrate | Zn²⁺ | NO₃⁻ | Zn(NO₃)₂ | Zn(NO₃)₂ |
✔ |
| Silver nitrate | Ag⁺ | NO₃⁻ | AgNO₃ | AgNO₃ |
✔ |
| Silver chromate | Ag⁺ | CrO₄²⁻ | Ag₂CrO₄ | Ag₂CrO₄ |
✔ |
All entries are correctly balanced.
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⚠️ Notes on Common Mistakes
-
Polyatomic ions: Always remember parentheses when multiple polyatomic ions are needed.
- Example: Ca(OH)₂ — not CaOH₂.
-
Roman numerals: Indicate the charge of transition metals (like Fe³⁺ vs Fe²⁺).
-
Subscripts: Only write numbers >1.
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✔ Conclusion
The
worksheet is correctly completed. Every chemical formula matches the charges of the ions and follows standard naming and formula-writing conventions.
If you were asked to
solve this worksheet, you would follow the steps above for each row. Since this is the
teacher's answer key, it can be used to check student work.
Would you like me to generate a
student version without answers, or help with any specific compound?
Parent Tip: Review the logic above to help your child master the concept of chemical formula writing worksheet.
