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Ch.10 - Chemical Bonding I: The Lewis Model
Chapter 10, Problem 64b

Write the Lewis structure for each molecule or ion. b. OH-

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Identify the total number of valence electrons in the hydroxide ion (OH<sup>-</sup>). Oxygen has 6 valence electrons, hydrogen has 1, and the negative charge adds 1 more electron, totaling 8 valence electrons.
Place the oxygen atom in the center and the hydrogen atom bonded to it, as hydrogen can only form one bond.
Draw a single bond between the oxygen and hydrogen atoms. This bond uses 2 of the 8 available valence electrons.
Distribute the remaining 6 valence electrons around the oxygen atom to satisfy its octet, placing them as lone pairs.
Ensure the structure reflects the negative charge by enclosing the structure in brackets and placing a negative sign outside the brackets.

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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 reactivity.
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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 atom's ability to form bonds, either by sharing electrons (covalent bonds) or transferring them (ionic bonds). For the hydroxide ion (OH⁻), knowing the valence electrons helps in constructing its Lewis structure.
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Formal Charge

Formal charge is a concept used to determine the charge distribution within a molecule or ion, calculated based on the number of valence electrons, the number of non-bonding electrons, and half the number of bonding electrons. It helps in assessing the stability of a Lewis structure. For the hydroxide ion, calculating formal charges can confirm that the structure is correct and that the overall charge is -1.
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