Textbook Question
For each molecule (a)–(f), indicate how many different electron-domain geometries are consistent with the molecular geometry shown. a.
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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 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?
Verified step by step guidance1
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.
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 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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01:53Formal Charge
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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01:33Molecular Geometry with Two Electron Groups
Related Practice
Textbook Question
The molecule shown here is difluoromethane 1CH2F22, which is used as a refrigerant called R-32. (c) If the molecule is polar, which of the following describes the direction of the overall dipole moment vector in the molecule: (i) from the carbon atom toward a fluorine atom, (ii) from the carbon atom to a point midway between the fluorine atoms, (iii) from the carbon atom to a point midway between the hydrogen atoms, or (iv) from the carbon atom toward a hydrogen atom?
Textbook Question
The following plot shows the potential energy of two Cl atoms as a function of the distance between them. (c) If the Cl2 molecule is compressed under higher and higher pressure, does the Cl–Cl bond become stronger or weaker?
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