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Ch.2 - Atoms, Molecules, and Ions
Chapter 2, Problem 69

Give the names and charges of the cation and anion in each of the following compounds: (a) CaO, (b) Na2SO4, (c) KClO4, (d) Fe1NO322, (e) Cr1OH23.

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1
Identify the cation and anion in each compound by breaking down the chemical formula into its constituent ions.
For (a) CaO: Recognize that calcium (Ca) is the cation with a charge of +2, and oxide (O) is the anion with a charge of -2.
For (b) Na2SO4: Identify sodium (Na) as the cation with a charge of +1, and sulfate (SO4) as the anion with a charge of -2.
For (c) KClO4: Determine that potassium (K) is the cation with a charge of +1, and perchlorate (ClO4) is the anion with a charge of -1.
For (d) Fe(NO3)2: Recognize iron (Fe) as the cation, and nitrate (NO3) as the anion. The charge on iron can be deduced from the formula, considering the charge of nitrate is -1. For (e) Cr(OH)3: Identify chromium (Cr) as the cation, and hydroxide (OH) as the anion. The charge on chromium can be deduced from the formula, considering the charge of hydroxide is -1.

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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 cations (positively charged ions) and anions (negatively charged ions). The electrostatic attraction between these oppositely charged ions holds the compound together. Understanding the composition of ionic compounds is essential for identifying the specific ions present in a given formula.
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Common Ions and Their Charges

Familiarity with common ions and their respective charges is crucial for determining the cations and anions in compounds. For example, calcium (Ca) typically forms a +2 cation, while oxide (O) forms a -2 anion. Similarly, sodium (Na) forms a +1 cation, and sulfate (SO4) forms a -2 anion. Recognizing these patterns aids in accurately naming the ions in various compounds.
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Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms that are covalently bonded and carry a net charge. Examples include sulfate (SO4^2-) and hydroxide (OH^-). Understanding polyatomic ions is essential for correctly identifying the components of compounds that contain them, as they often appear in more complex ionic compounds.
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