Molecules with the same molecular formulas but different structural formulas are called isomers.

There are different types of isomers, including:

* Structural isomers: These have the same atoms but in different bonding arrangements.

* Stereoisomers: These have the same bonding arrangement but differ in the spatial arrangement of their atoms.

* Enantiomers: These are non-superimposable mirror images of each other.

* Diastereomers: These are stereoisomers that are not mirror images of each other.

Isomers often have different physical and chemical properties due to their distinct structures.