Use electronegativity to determine the polarity of a covalent bond. Predict the polarity of molecules by using a combination of molecular shape and electronegativity. Use valence bond theory to describe the bonding in covalent molecules. Describe how sigma and pi bonds are formed. Understand the theory of orbital hybridization and how it relates to molecular structure.
Gases are very important to living systems.
Animals need to breathe air in order to obtain oxygen to support life. Plants require carbon dioxide in the photosynthesis process. There are many other important gaseous substances that we use in one way or another. For example, chlorine gas is used to purify water, acetylene is used for welding, and propane is used for heating and cooking. The other two states of matter, liquids and solids, are vastly different from gases.