Final answer:
Stereoisomers with two asymmetric centers that have opposite configurations at each center are called enantiomers. Enantiomers are non-superimposable mirror images. If they differ at only one asymmetric center, they are known as diastereomers.
Step-by-step explanation:
Stereoisomers with two asymmetric centers are called enantiomers if the configuration of both asymmetric centers in one stereoisomer is the opposite of the configuration of the asymmetric centers in the other stereoisomer.
A stereocenter is a carbon atom bonded to four different groups, and when a molecule has two stereocenters, there can be up to four different stereoisomers possible. When each stereocenter has the opposite configuration in two stereoisomers, they are mirror images of each other and are referred to as enantiomers. These molecules are non-superimposable, meaning that they cannot be placed on top of each other and give the same molecule.
However, when the two stereoisomers differ in their configuration at only one of the two asymmetric centers, these are known as diastereomers. Diastereomers are not mirror images of each other and have different physical properties.