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Ch.2 - Atoms, Molecules, and Ions
Chapter 2, Problem 70a

Give the names and charges of the cation and anion in each of the following compounds: (a) CuS

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Identify the elements present in the compound CuS. Cu represents copper, and S represents sulfur.
Determine the common oxidation states for each element. Copper typically has oxidation states of +1 or +2, and sulfur typically has an oxidation state of -2.
Based on the formula CuS, infer the charges of the ions. Since there is one copper atom and one sulfur atom, and the compound is neutral, copper must be balancing the charge of sulfur.
Assign the charge to the copper cation. Since sulfur usually has a charge of -2, copper in this compound must have a charge of +2 to balance the overall charge.
Conclude that in the compound CuS, the cation is copper with a charge of +2 (Cu^2+), and the anion is sulfur with a charge of -2 (S^2-).

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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 charged particles known as ions. These compounds typically consist of a cation (positively charged ion) and an anion (negatively charged ion). Understanding the nature of ionic bonds is essential for identifying the components of a compound like CuS.
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Cation and Anion Identification

Cations are usually metals that lose electrons, resulting in a positive charge, while anions are typically nonmetals that gain electrons, leading to a negative charge. In the case of CuS, recognizing the oxidation states of copper and sulfur is crucial for determining which is the cation and which is the anion.
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Oxidation States

Oxidation states indicate the degree of oxidation of an atom in a compound, helping to determine the charge of ions. For example, copper can have multiple oxidation states, commonly +1 or +2, while sulfur typically has a -2 oxidation state in sulfides. Knowing these states is vital for accurately naming the ions in CuS.
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