SAT Subject Test Chemistry
REVIEW OF MAJOR TOPICS
SIGMA AND PI BONDS
When bonding occurs between s and p orbitals, each bond is identified by a special term. A sigma bond is a bond between s orbitals, or an s orbital and another orbital such as a p orbital. It includes bonding between hybrids of s orbitals such as sp, sp2, and sp3.
In the methane molecule, the sp3 orbitals are each bonded to hydrogen atoms. These are sigma bonds.
When two p orbitals share electrons in a covalent bond, the result is a pi bond. Here is an example:
Chapter 14 gives more examples of sigma and pi bonding.