What is the charge on the Cr in the ionic compound Cr2O3?
The correct answer and explanation is:
The charge on chromium (Cr) in the ionic compound Cr₂O₃ is +3.
Here’s how to determine this:
- Oxygen’s Charge: In most ionic compounds, oxygen typically has a charge of -2. Since Cr₂O₃ contains three oxygen atoms, the total charge contributed by the oxygen ions is 3×−2=−63 \times -2 = -6.
- Balancing the Charges: The overall compound must be electrically neutral, meaning the total positive charge must balance the total negative charge. Since the oxygen ions contribute -6 in total, the chromium ions must contribute +6 to balance the charge.
- Chromium’s Charge: The compound contains two chromium atoms, so to balance the -6 charge from the oxygen, each chromium atom must have a charge of +3. This is because 2×+3=+62 \times +3 = +6, which balances the -6 charge from the oxygen ions.
Thus, each chromium ion in Cr₂O₃ has a charge of +3.
To summarize:
- Oxygen is -2.
- Two chromium ions must balance the -6 charge from oxygen, so each chromium ion has a charge of +3.
- The ionic compound Cr₂O₃ is electrically neutral, with the total positive charge (+6) balancing the total negative charge (-6).