Chapter 5.8, Problem 1QQ

Interpretation Introduction

Interpretation:

The geometrical arrangement that minimize the repulsion that occurs among the three valence electron pairs present on the central atom in VSEPR theory has to be chosen from the given options.

Concept Introduction:

Information about the number of bonds and types of bonds can be obtained from Lewis structure but the molecular geometry cannot be obtained.  Three dimensional arrangement of atoms in a molecule can be given by molecular geometry.  Physical and chemical properties are determined by the molecular geometry of the molecule.

Using VSEPR theory and Lewis structure, the molecular geometry of the molecule that contain less number of atoms can be predicted.  VSEPR theory uses the information from Lewis structure of the molecule to predict the molecular geometry of the molecule.  Main concept of VSEPR theory is that electron pairs that are present in the valence shell adopt arrangement in a way that minimize the repulsion between like charges.

If the central atom contains two electron pairs, then it has to be far apart means, it has to be on opposite side of the nucleus.  This means the angle has to be $180°$ between them.  This type of arrangement for electron pair result in linear.

If the central atom contains three electron pairs, then it has to be far apart means, it has to be on corner of a triangle.  This means the angle has to be $120°$ between them.  This type of arrangement for electron pair result in trigonal planar.

If the central atom contains four electron pairs, then it has to be far apart means, it has to be in a tetrahedral arrangement.  This means the angle has to be $109°$ between them.  This type of arrangement for electron pair result in tetrahedral.

The collection of valence electron that is present in localized region about central atom in a molecule is known as VSEPR electron group.  This may contain two electrons, four electrons, or six electrons.  The electron group that contain four and six electrons repel each other.