What defines an isomer?

An isomer is defined as a compound that contains the same number and types of atoms but has a different arrangement of those atoms. This difference in arrangement can lead to distinct physical and chemical properties between the isomers, even though they may share the same molecular formula. For example, butane (C4H10) can exist as two isomers: n-butane and isobutane. They both have the same chemical formula but differ in their structural arrangements.

The concept of isomerism is crucial in chemistry as it explains how molecules with the same composition can exhibit a variety of behaviors and characteristics based on their structural configuration. This principle underlies many important concepts in organic chemistry, biology, and materials science, highlighting the significance of atomic arrangement in determining a compound’s properties and reactivity.