Deducing the ions in a binary ionic compound Complete the table below by writing the symbols for the ionic cation and anion compound. | Compound | Ionic Cation | Ionic Anion | |———-|————–|————-| | NaCl | Na | Cl | | FeF2 | Fe | F | | FeCl2 | Fe | Cl | | AgBr | Ag | Br | | Cr2O3 | Cr | O |
The Correct Answer and Explanation is:
Here is the corrected version of the table based on the proper ionic charges of the elements involved:
| Ionic Compound | Cation | Anion |
|---|---|---|
| NaCl | Na⁺ | Cl⁻ |
| FeF₃ | Fe³⁺ | F⁻ |
| FeI₂ | Fe²⁺ | I⁻ |
| AgBr | Ag⁺ | Br⁻ |
| CrO₂ | Cr⁴⁺ | O²⁻ |
Explanation
In binary ionic compounds, the overall charge must be neutral, which means the total positive charge from the cations must balance the total negative charge from the anions. To deduce the charges of ions in compounds, we use the known charges of common ions and simple arithmetic.
1. NaCl: Sodium (Na) is an alkali metal in Group 1, always forming a +1 ion (Na⁺). Chlorine (Cl) is a halogen in Group 17, forming a −1 ion (Cl⁻). One Na⁺ and one Cl⁻ combine to form NaCl, a neutral compound.
2. FeF₃: Fluoride (F⁻) has a −1 charge. Since there are 3 fluoride ions, the total negative charge is −3. To balance it, iron (Fe) must be +3 (Fe³⁺).
3. FeI₂: Iodide (I⁻) also carries a −1 charge. Two I⁻ ions make −2 total, so iron must be Fe²⁺ to balance the charge.
4. AgBr: Silver (Ag) typically forms a +1 ion (Ag⁺), and bromide (Br⁻) is −1. They combine in a 1:1 ratio to form a neutral compound.
5. CrO₂: Oxygen (O) has a −2 charge (O²⁻). Two O²⁻ ions give a total of −4. To balance this, chromium (Cr) must be +4 (Cr⁴⁺). Thus, CrO₂ contains Cr⁴⁺ and O²⁻ ions.
Understanding how to deduce ionic charges from the formula is essential for correctly writing chemical formulas and predicting chemical reactions. This involves knowledge of periodic trends and oxidation states, especially for transition metals like Fe and Cr, which can exhibit multiple possible charges.
