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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 67b

Predict the molecular geometry of each of the following molecules: (b) H O C O C O O H
Chemical structure of a molecule with labeled atoms for predicting molecular geometry.

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Identify the central atoms in the molecule. In this case, the central atoms are carbon (C) and nitrogen (N).
Determine the number of electron groups around each central atom. For carbon (C), there are three groups: one double bond with oxygen (O), one single bond with hydrogen (H), and one single bond with nitrogen (N). For nitrogen (N), there are four groups: one lone pair, two single bonds with hydrogen (H), and one single bond with carbon (C).
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. For carbon (C) with three electron groups, the geometry is trigonal planar. For nitrogen (N) with four electron groups, the geometry is tetrahedral.
Adjust the geometry for lone pairs. For nitrogen (N), the presence of one lone pair changes the tetrahedral geometry to a trigonal pyramidal geometry.
Summarize the molecular geometries: Carbon (C) has a trigonal planar geometry, and nitrogen (N) has a trigonal pyramidal geometry.

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Key Concepts

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

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to VSEPR, electron pairs will arrange themselves as far apart as possible to minimize repulsion, leading to specific molecular shapes such as linear, trigonal planar, or tetrahedral.
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Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate the bonding and lone pairs of electrons in a molecule. For example, in the case of carbon in the given molecule, sp2 hybridization occurs, resulting in a trigonal planar arrangement around the carbon atom, which influences the overall molecular geometry.
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Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is determined by the number of bonding pairs and lone pairs of electrons around the central atom, which affects the angles between bonds and the overall shape. Understanding molecular geometry is crucial for predicting the physical and chemical properties of substances.
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