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Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory
Chapter 11, Problem 40d

Determine the molecular geometry and sketch each molecule or ion, using the bond conventions shown in “Representing Molecular Geometries on Paper” in Section 11.4. d. IF2–

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Determine the total number of valence electrons in the molecule. Iodine (I) has 7 valence electrons, each fluorine (F) has 7 valence electrons, and the negative charge adds 1 more electron.
Calculate the total number of valence electrons: 7 (I) + 2*7 (F) + 1 (negative charge) = 22 valence electrons.
Use the VSEPR theory to determine the electron pair geometry. Iodine is the central atom, and it will have 2 bonding pairs and 3 lone pairs, which corresponds to a trigonal bipyramidal electron pair geometry.
Determine the molecular geometry by considering only the positions of the atoms (bonding pairs). With 2 bonding pairs and 3 lone pairs, the molecular geometry is linear.
Sketch the molecule using the bond conventions: represent the linear shape with the central iodine atom and two fluorine atoms on opposite sides, indicating the lone pairs around iodine.

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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 to minimize repulsion, leading to specific molecular shapes. This theory is essential for determining the geometry of molecules like IF2–.
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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. For the IF2– ion, understanding its molecular geometry helps in visualizing how the iodine and fluorine atoms are spatially oriented, which is crucial for sketching the molecule accurately.
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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 provide a visual representation of the arrangement of electrons and help in predicting molecular geometry. For IF2–, drawing the Lewis structure is the first step in determining its shape and understanding the distribution of charge within the ion.
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