Multiple Choice
In the chemical formula for an ionic compound, which ion is written first?
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3. Chemical Reactions
Naming Ionic Compounds
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Which of the following is the correct chemical formula for aluminum oxide?
A
Al2O3
B
AlO2
C
Al3O2
D
AlO
Verified step by step guidance1
Identify the charges of the ions involved: aluminum typically forms a +3 charge (Al^{3+}), and oxygen typically forms a -2 charge (O^{2-}).
Determine the ratio of aluminum ions to oxide ions needed to balance the total positive and negative charges so that the compound is electrically neutral.
Set up the charge balance equation: (number of Al ions) \times (+3) + (number of O ions) \times (-2) = 0.
Find the smallest whole number ratio of Al to O that satisfies the charge balance. This involves finding the least common multiple of the charges 3 and 2, which is 6.
Write the chemical formula using the ratio found: since 2 Al^{3+} ions contribute +6 charge and 3 O^{2-} ions contribute -6 charge, the formula is Al_{2}O_{3}.
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