Question

Write the formulas for the ionic compounds formed by each of the following pairs
sodium ions and sulfate ions
Pb4+ and Po43-
iron(III) ions and chloride ions
K+ and Cr2O7-2

Answer 1

To write the formulas for the ionic compounds formed by the given pairs of ions, we need to balance the charges of the ions involved.

1. **Sodium ions (Na⁺) and sulfate ions (SO₄²⁻)**:
- Sodium ion has a charge of +1.
- Sulfate ion has a charge of -2.
- To balance the charges, we need 2 sodium ions for every sulfate ion:
- **Formula:** Na₂SO₄

2. **Lead(IV) ions (Pb⁴⁺) and phosphate ions (PO₄³⁻)**:
- Lead(IV) ion has a charge of +4.
- Phosphate ion has a charge of -3.
- To balance the charges, we need 3 lead(IV) ions and 4 phosphate ions:
- **Formula:** Pb₃(PO₄)₄ or you can also write it as Pb₄PO₄.

3. **Iron(III) ions (Fe³⁺) and chloride ions (Cl⁻)**:
- Iron(III) ion has a charge of +3.
- Chloride ion has a charge of -1.
- To balance the charges, we need 3 chloride ions for every iron(III) ion:
- **Formula:** FeCl₃

4. **Potassium ions (K⁺) and dichromate ions (Cr₂O₇²⁻)**:
- Potassium ion has a charge of +1.
- Dichromate ion has a charge of -2.
- To balance the charges, we need 2 potassium ions for every dichromate ion:
- **Formula:** K₂Cr₂O₇

**In summary:**
1. Na₂SO₄
2. Pb₃(PO₄)₄
3. FeCl₃
4. K₂Cr₂O₇