What term describes compounds that have the same molecular formula but different structural formulas?

The term that describes compounds with the same molecular formula but different structural formulas is structural isomers. These isomers can vary in how their atoms are connected or arranged, leading to different chemical properties.

To elaborate, structural isomers differ from one another in the connectivity of their atoms. For example, butane (C4H10) can exist as two isomers: n-butane, which is a straight-chain structure, and isobutane, which is a branched structure. Though they have the same molecular formula, their distinct structural arrangements give them different physical and chemical properties.

In contrast, functional isomers refer to compounds that have the same molecular formula but differ in the functional group present, which also constitutes a type of structural isomerism but is more specific. Cis-trans isomers and stereoisomers pertain to differences in three-dimensional arrangements (stereochemistry) rather than basic structural differences in bonding or connectivity.