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Ch.10 - Chemical Bonding II: Molecular Shapes & Valence Bond Theory
Chapter 10, Problem 4

What is the molecular geometry of BrF5, and how can it be sketched using the bond conventions shown in 'Representing Molecular Geometries on Paper' in Section 10.4?

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1
Determine the total number of valence electrons in BrF_5. Bromine (Br) has 7 valence electrons, and each fluorine (F) has 7 valence electrons. Calculate the total for BrF_5.
Draw the Lewis structure for BrF_5. Place Br in the center and arrange the 5 F atoms around it, using single bonds. Distribute the remaining electrons to satisfy the octet rule for each F atom.
Identify the electron pair geometry. BrF_5 has 6 regions of electron density (5 bonding pairs and 1 lone pair), which corresponds to an octahedral electron pair geometry.
Determine the molecular geometry. With one lone pair, the molecular geometry of BrF_5 is square pyramidal.
Sketch the molecular geometry using bond conventions. Represent the square pyramidal shape with Br at the center, 4 F atoms forming a square plane, and the 5th F atom above the plane. Use solid lines for bonds in the plane, a wedge for the bond coming out of the plane, and a dashed line for the bond going into the plane.

Key Concepts

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

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 influence the shape due to repulsion between electron pairs. Understanding molecular geometry is crucial for predicting the physical and chemical properties of a substance.
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VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of 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. For BrF5, the presence of five bonding pairs and one lone pair results in a square pyramidal geometry.
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Bond Conventions in Molecular Sketching

Bond conventions in molecular sketching involve using specific symbols and notations to represent atoms, bonds, and lone pairs in a molecule. Common conventions include solid lines for bonds in the plane, dashed lines for bonds going behind the plane, and wedged lines for bonds coming out of the plane. These conventions help accurately depict the three-dimensional structure of molecules like BrF5 when sketching.
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