We are surrounded by color; indoors there are the varied colors of paint,
fabrics, and the many hues of the screens on our computers, television
sets, and telephones. Outdoors there are the colors of vegetation and the
changing colors of the seasons. Chemists learned that the colors of many natural
pigments are due to the presence of organic compounds with common structural
features. They discovered how small differences in the structures of the molecules
of these compounds can enhance photosynthesis and attract pollinating bees. We
now know how the shapes of molecules and the orbitals occupied by their electrons
explain the properties of these compounds and even the processes taking
place in our eyes that allow us to see them.
The impact of modern theories of bonding, however, goes far beyond understanding
how molecules are responsible for different colors. Scientists’ increasing
knowledge of the electronic structures of the atoms and molecules in polymers and
semiconductors has led to the development of new technologies. The pharmaceutical
industry is increasingly turning to computer-aided design—in which molecular
shape and the distribution of electrons play a crucial role—to discover new, more
potent drugs (BOX 4.1).