Ch.2 - Atoms, Molecules, and Ions

Brown - Chemistry: The Central Science 14th Edition

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Brown 14th Edition

Ch.2 - Atoms, Molecules, and Ions

Problem 59d

Chapter 2, Problem 59d

Using the periodic table to guide you, predict the chemical formula and name of the compound formed by the following elements: (d) K and S.

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Identify the elements involved: Potassium (K) and Sulfur (S).

Determine the charges of the ions each element forms: Potassium (K) is in Group 1 and forms a K⁺ ion, while Sulfur (S) is in Group 16 and forms an S²⁻ ion.

Balance the charges to ensure the compound is neutral: You need two K⁺ ions to balance one S²⁻ ion, resulting in a neutral compound.

Write the chemical formula by combining the ions in the correct ratio: The formula is K₂S.

Name the compound: The name is Potassium Sulfide, following the convention of naming the metal first and the non-metal with an '-ide' suffix.

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Key Concepts

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

Ionic Bonding

Ionic bonding occurs when atoms transfer electrons to achieve full outer electron shells, resulting in the formation of charged ions. In this case, potassium (K) donates one electron to become K⁺, while sulfur (S) accepts two electrons to become S²⁻. The electrostatic attraction between these oppositely charged ions leads to the formation of an ionic compound.

Chemical Formula

A chemical formula represents the ratio of elements in a compound. For potassium and sulfur, the charges of the ions must balance. Since K has a +1 charge and S has a -2 charge, two potassium ions are needed to balance one sulfur ion, resulting in the formula K₂S. This indicates that the compound consists of two potassium ions for every one sulfur ion.

Nomenclature of Ionic Compounds

The nomenclature of ionic compounds involves naming the cation (positive ion) first, followed by the anion (negative ion). For K₂S, the cation is potassium, and the anion is sulfide. Therefore, the compound is named potassium sulfide, reflecting the elements involved and their respective charges in the compound.

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