Isomers are fascinating molecules that share the same molecular formula but differ in their connectivity or spatial arrangement. There are two primary categories of isomers: structural (or constitutional) isomers and stereoisomers.

Structural isomers have the same molecular formula but differ in how the atoms are connected. For example, consider the molecular formula C₄H₈. One structural isomer could have four carbon atoms arranged in a straight chain, while another could feature three carbon atoms in a chain with a fourth carbon branching off. Additionally, structural isomers can include variations such as double bonds, which further alter the connectivity of the atoms.

Stereoisomers, on the other hand, maintain the same molecular formula and connectivity but differ in their spatial orientation. Using the same C₄H₈ example, a stereoisomer would have the same chain of four carbon atoms, with a double bond between two of them. However, in this case, the orientation of the atoms around the double bond would differ; for instance, one carbon could be oriented upwards while the other is oriented downwards, creating a distinct spatial arrangement.

In summary, isomers can be categorized into structural isomers, which differ in connectivity, and stereoisomers, which differ in spatial orientation. Understanding these differences is crucial in the study of organic chemistry, as the properties and reactivity of isomers can vary significantly based on their structure and arrangement.