http://www.ck12.org Chapter 9. Covalent Bonding
9.2 Molecular Geometry
Lesson Objectives
- Explain the basis of VSEPR theory.
- Predict the shapes of molecules and polyatomic ions using VSEPR theory.
- Account for variations in bond angles based on the relative repulsive forces exerted by lone pairs and bonding
pairs of electrons. - Describe the relationship between molecular geometry and electron domain geometry.
Lesson Vocabulary
- molecular geometry: The three-dimensional arrangement of atoms in a molecule.
- valence shell: The outermost occupied shell of electrons in an atom.
- valence shell electron pair repulsion (VSEPR) theory: States that a molecule will adjust its shape so that
the valence electron pairs stay as far apart from each other as possible. - electron domain geometry: The number of atoms bonded to the central atom plus the number of lone pairs
on the central atom.
Check Your Understanding
Recalling Prior Knowledge
- How are Lewis electron dot structures determined?
- What are bonding pairs of electrons and what are lone pairs?
Introduction
Molecular geometryis the three-dimensional arrangement of atoms in a molecule. The molecular geometry, or
shape, of a molecule is an important factor that affects the physical and chemical properties of a compound. Those
properties include melting and boiling points, solubility, density, and the types of chemical reactions that a compound
undergoes. In this lesson, you will learn a technique to predict molecular geometry based on a molecule’s Lewis
electron dot structure.