alleryStart learning →The formula Al2O3 tells you the compound contains two aluminium cations for every:
AJust one oxide anion
BSix oxide anion units
CThree oxide anions
DTwo oxide anions
Answer & Solution
Correct answer: C. Three oxide anions
1. An ionic formula is fixed by the requirement that total charge be zero.
2. The formula for aluminium oxide indicates that this ionic compound contains two aluminium cations for every three oxide anions.
3. Two ions of charge plus three and three of charge minus two sum to zero.
4. The formula gives the ratio, not the physical arrangement of the ions.
_Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 7 'Chemical Bonding and Molecular Geometry', sections 7.1-7.6_
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