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Ch.10 - Chemical Bonding I: The Lewis Model
Chapter 10, Problem 54

Write the Lewis structure for each molecule. a. CH2O b. C2Cl4 c. CH3NH2 d. CFCl3 (C central)

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1. Identify the total number of valence electrons for each molecule. For example, in CH2O, Carbon has 4 valence electrons, Hydrogen has 1 each (total 2 for 2 Hydrogen atoms), and Oxygen has 6. So, the total number of valence electrons is 4+2+6=12.
2. Draw a skeleton structure of the molecule, placing the least electronegative atom in the center (usually Carbon). Hydrogen and Fluorine are usually terminal atoms. For example, in CH2O, the skeleton would be H-C-O-H.
3. Distribute the valence electrons among the atoms, starting with the outer atoms first. Each bond counts as 2 electrons. Make sure each atom (except Hydrogen) has an octet (8 electrons). For example, in CH2O, after forming single bonds between C-H, C-O, and O-H, we have 4 electrons left. We place these on the Oxygen atom to complete its octet.
4. If there are not enough electrons to give every atom an octet, try multiple bonds (like double or triple bonds). For example, in CH2O, we can form a double bond between Carbon and Oxygen to satisfy the octet rule for Carbon.
5. Repeat these steps for each molecule: C2Cl4, CH3NH2, and CFCl3.

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Key Concepts

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

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent valence electrons and lines to represent bonds between atoms. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting the behavior of molecules in chemical reactions.
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Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial in determining how atoms bond with each other. The number of valence electrons influences the molecule's reactivity and stability. In Lewis structures, it is important to account for all valence electrons to ensure that the structure accurately represents the molecule's electron configuration.
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Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is influenced by the number of bonds and lone pairs around the central atom, which can affect the molecule's physical and chemical properties. Understanding molecular geometry is vital for predicting the behavior of molecules in reactions and their interactions with other substances.
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