The Good, the Bad, and the Unlikely: Molecules in the Atmosphere

 

Using Lewis Dot Structures and VSEPR to Understand Bonding and to

Predict Shapes of Molecules.

 

 

 

Introduction

 

There are countless ways in which atoms might associate with other atoms to form molecules and compounds. As the number of atoms in a molecule increases, the possibilities for complexity increase rapidly. Certain key questions arise:

 

1. How are atoms connected to other atoms?

 

2. How can we decide which ways to arrange these atoms?

 

3. Is there a concise set of rules or guidelines for building molecules which is easy and practical to apply, especially for introductory student of chemistry?

 

4. Are there rules which allow us to predict the overall 3-dimensional shape of a molecule?

 

5. What is the experimental basis and support for these guidelines?

 

 

 

Using specific examples, we can ask such questions as:

• Why do hydrogen and chlorine form a simple diatomic molecule?

• How do the binary hydrides of carbon, nitrogen, and oxygen compare in bonding and structure?

• Why are the Group 8 elements generally not reactive?

• Why do both carbon monoxide and carbon dioxide form stable molecules?

• How does oxygen exist in two distinct elemental forms, dioxygen and ozone?

• Why do potassium and chlorine form an ionic salt but chlorine and phosphorus form a covalent molecule?

• Why does a triatomic molecule like water have a bent shape, whereas triiodide is linear?

• How can sulfur and oxygen associate to form sulfur dioxide or sulfate ion?

• Why does phosphorus pentachloride contain two types of bond angles?

• Do isoelectronic species, like carbon monoxide and dinitrogen or nitrate and carbonate, have similar bonding and shapes?