Unshared, or lone, electron pairs play an important role in determining the chemical and physical properties of organic compour Thus, it is important to know which atoms carry unshared pairs.
Use the structural formulas below to determine the number of unshared pairs at each designated atom.
Be sure your answers are consistent with the formal charges on the formulas.
The number of unshared pairs at atom $\mathbf{a}$ is $\square$ The number of unshared pairs at atom $\mathbf{b}$ is $\square$ The number of unshared pairs at atom $\mathbf{c}$ is $\square$ The number of unshared pairs at atom $\mathbf{a}$ is $\square$ The number of unshared pairs at atom $\mathbf{b}$ is $\square$
The number of unshared pairs at atom $\mathbf{c}$ is $\square$

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∻Solution∻ ‖ 1 ⋮ **Determine the number of unshared pairs for atom a (nitrogen)**: Nitrogen typically forms three bonds and has one unshared pair of electrons to satisfy the octet rule. Given that nitrogen is triple-bonded to carbon and carries a positive charge, it has no unshared pairs of electrons. ‖ ‖ 2 ⋮ **Determine the number of unshared pairs for atom b (central carbon)**: Carbon forms four bonds to satisfy the octet rule. In this molecule, carbon is triple-bonded to nitrogen and double-bonded to oxygen, which accounts for all four bonds without any unshared pairs of electrons. ‖ ‖ 3 ⋮ **Determine the number of unshared pairs for atom c (oxygen)**: Oxygen typically forms two bonds and has two unshared pairs of electrons to satisfy the octet rule. Given that oxygen is double-bonded to carbon and carries a negative charge, it has one unshared pair of electrons. ‖ ‖ 4 ⋮ **Determine the number of unshared pairs for atom a (oxygen in the second molecule)**: Oxygen typically forms two bonds and has two unshared pairs of electrons. Since it is single-bonded to carbon, it has three unshared pairs of electrons. ‖ ‖ 5 ⋮ **Determine the number of unshared pairs for atom b (carbon in the second molecule)**: Carbon forms four bonds to satisfy the octet rule. Since it is bonded to one oxygen and three hydrogen atoms, it has no unshared pairs of electrons. ‖ ‖ 6 ⋮ **Determine the number of unshared pairs for atom c (carbon in the second molecule)**: This carbon is identical to atom b, bonded to one oxygen and three hydrogen atoms, and also has no unshared pairs of electrons. ‖ ∻1 Answer∻ ⚹ The number of unshared pairs at atom $\mathbf{a}$ is 0 ⚹ ⚹ The number of unshared pairs at atom $\mathbf{b}$ is 0 ⚹ ⚹ The number of unshared pairs at atom $\mathbf{c}$ is 1 ⚹ ∻2 Answer∻ ⚹ The number of unshared pairs at atom $\mathbf{a}$ is 3 ⚹ ⚹ The number of unshared pairs at atom $\mathbf{b}$ is 0 ⚹ ⚹ The number of unshared pairs at atom $\mathbf{c}$ is 0 ⚹ ∻Key Concept∻ ⚹ Unshared pairs of electrons are determined by the octet rule and the bonding preferences of atoms in molecules. ⚹ ∻Explanation∻ ⚹ Nitrogen with a positive charge has no unshared pairs, carbon with four bonds has no unshared pairs, and oxygen with a negative charge has one unshared pair in the first molecule. In the second molecule, oxygen with a single bond has three unshared pairs, while both carbons with four bonds have no unshared pairs. ⚹◊What is the relationship between the number of unshared electron pairs and the formal charges on the atoms in a molecule?⍭ Generate me a similar question◊

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