SAT Subject Test Chemistry

PART 2

REVIEW OF MAJOR TOPICS

CHAPTER 3

Bonding

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.