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Ch.10 - Chemical Bonding I: The Lewis Model
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook
All textbooksTro 6th EditionCh.10 - Chemical Bonding I: The Lewis ModelProblem 40b
Chapter 10, Problem 40b

Write the Lewis symbols for the ions in each ionic compound. b. Li2S

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Step 1: Identify the ions in the compound. In Li2S, the ions are Li+ (lithium ion) and S2- (sulfide ion).
Step 2: Write the Lewis symbol for the lithium ion. The Lewis symbol for an atom shows the symbol of the element and its valence electrons. Lithium (Li) has one valence electron, but as a Li+ ion, it has lost this electron. Therefore, the Lewis symbol for Li+ is just Li with no dots around it.
Step 3: Write the Lewis symbol for the sulfide ion. Sulfur (S) has six valence electrons, but as a S2- ion, it has gained two additional electrons for a total of eight. Therefore, the Lewis symbol for S2- is S surrounded by eight dots, arranged in pairs to represent the filled s and p orbitals.
Step 4: Combine the Lewis symbols for the ions to represent the ionic compound. In Li2S, there are two Li+ ions for each S2- ion. Therefore, the Lewis symbols for the ions in Li2S are two Li symbols (with no dots) and one S symbol (with eight dots).
Step 5: Remember that Lewis symbols represent the arrangement of valence electrons, and ionic compounds are formed when atoms transfer electrons to achieve a full outer electron shell. The Lewis symbols for the ions in an ionic compound can help you visualize this electron transfer.

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Key Concepts

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

Lewis Symbols

Lewis symbols, or Lewis dot structures, represent the valence electrons of an atom as dots around the element's symbol. This notation helps visualize how atoms bond and interact in chemical compounds. For ions, the Lewis symbol indicates the gain or loss of electrons, showing the resulting charge on the ion.
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Ionic Compounds

Ionic compounds are formed through the electrostatic attraction between positively charged cations and negatively charged anions. In the case of Li<sub>2</sub>S, lithium (Li) donates electrons to sulfur (S), resulting in Li<sup>+</sup> ions and S<sup>2-</sup> ions. Understanding the formation of these ions is crucial for drawing their Lewis symbols.
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Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. For lithium, the electron configuration is 1s<sup>2</sup> 2s<sup>1</sup>, indicating it has one valence electron available for bonding. This concept is essential for determining how many electrons are lost or gained when forming ions, which directly influences the Lewis symbols.
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