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Ch.9 - Molecular Geometry and Bonding Theories
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
9장, 문제 1

Sodium azide is a shock-sensitive compound that releases N2 upon physical impact. The compound is used in automobile airbags. The azide ion is N3-. (a) Draw the Lewis structure of the azide ion that minimizes the formal charge (it does not form a triangle). Is it linear or bent?

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Step 1: Count the total number of valence electrons for the azide ion (N3^-). Each nitrogen atom has 5 valence electrons, and the ion has an extra electron due to the negative charge, giving a total of 16 valence electrons.
Step 2: Arrange the nitrogen atoms in a linear sequence (N-N-N) since the problem specifies that it does not form a triangle. Distribute the electrons to form bonds and satisfy the octet rule for each nitrogen atom.
Step 3: Start by placing a single bond between each pair of nitrogen atoms (N-N-N), using 4 electrons. Distribute the remaining 12 electrons to satisfy the octet rule, starting with the outer nitrogen atoms.
Step 4: Assign lone pairs to the outer nitrogen atoms first, then adjust the bonding to minimize formal charges. Consider forming double or triple bonds if necessary to achieve the lowest possible formal charges.
Step 5: Calculate the formal charge for each nitrogen atom using the formula: Formal Charge = (Valence electrons) - (Non-bonding electrons) - (Bonding electrons/2). Adjust the structure to ensure the formal charges are minimized, ideally achieving a structure where the formal charges are as close to zero as possible.

주요 개념

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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 help visualize the arrangement of electrons and the connectivity of atoms, allowing chemists to predict molecular geometry and reactivity. In the case of the azide ion (N3-), drawing the correct Lewis structure is essential to determine its formal charges and overall stability.
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04:28
Lewis Dot Structures: Ions

Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, 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 most stable Lewis structure by minimizing the formal charges across the molecule. For the azide ion, minimizing formal charge is crucial to identify the most stable resonance structure.
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Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule, which is influenced by the repulsion between electron pairs according to VSEPR (Valence Shell Electron Pair Repulsion) theory. The azide ion, with its linear arrangement of atoms, exhibits a geometry that can be predicted from its Lewis structure. Understanding whether a molecule is linear or bent is key to predicting its physical and chemical properties.
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01:33
Molecular Geometry with Two Electron Groups