Multiple Choice
Which of the following is the correct formula for the ionic compound formed between Na^+ and PO_4^{3-} ions?
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3. Chemical Reactions
Writing Ionic Compounds
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Which of the following is the correct chemical formula for aluminum iodide?
A
Al2I3
B
Al3I2
C
AlI
D
AlI3
Verified step by step guidance1
Identify the charges of the ions involved: aluminum typically forms a +3 charge (Al^{3+}), and iodide forms a -1 charge (I^{-}).
Determine the ratio of ions needed to balance the overall charge so that the compound is electrically neutral.
Since aluminum has a +3 charge and iodide has a -1 charge, you need three iodide ions to balance one aluminum ion.
Write the chemical formula by placing the number of each ion as subscripts: one aluminum ion and three iodide ions, resulting in AlI_{3}.
Verify that the total positive charge (+3 from Al) balances the total negative charge (3 × -1 from I), confirming the formula AlI_{3} is correct.
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