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Ch.2 - Atoms, Molecules, and Ions
Chapter 2, Problem 61d

Predict the chemical formulas of the ionic compound formed by (d) Li+ and PO43-

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Identify the charges of the ions involved: Li^+ has a charge of +1 and PO_4^{3-} has a charge of -3.
To form a neutral ionic compound, the total positive charge must balance the total negative charge.
Determine the number of Li^+ ions needed to balance the charge of one PO_4^{3-} ion. Since Li^+ has a +1 charge, you will need three Li^+ ions to balance the -3 charge of one PO_4^{3-} ion.
Write the chemical formula by placing the cation (Li^+) first, followed by the anion (PO_4^{3-}). Use subscripts to indicate the number of each ion needed to balance the charges.
The chemical formula of the compound is Li_3PO_4, indicating three lithium ions for every phosphate ion.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Compounds

Ionic compounds are formed when atoms transfer electrons, resulting in the formation of positively charged cations and negatively charged anions. The electrostatic attraction between these oppositely charged ions leads to the creation of a stable compound. Understanding the charges of the ions involved is crucial for predicting the correct formula of the resulting ionic compound.
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Charge Balance

In ionic compounds, the total positive charge must balance the total negative charge to achieve electrical neutrality. This means that the ratio of cations to anions must be adjusted so that their combined charges equal zero. For example, if a cation has a +1 charge and an anion has a -3 charge, three cations would be needed to balance one anion, resulting in a formula of Li3PO4.
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Chemical Formula Representation

The chemical formula of an ionic compound represents the types and ratios of ions present in the compound. It is typically written with the cation first followed by the anion. The subscripts indicate the number of each type of ion needed to maintain charge balance, providing a clear and concise way to convey the composition of the compound.
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