What type of isomerism occurs when compounds have the same molecular formula but different connectivity?

The correct answer is structural isomerism because this type of isomerism involves compounds that share the same molecular formula but differ in the way their atoms are connected to one another. Structural isomers can have significantly different physical and chemical properties due to the varying arrangements of atoms within the molecules.

Stereoisomerism, on the other hand, refers to isomers that have the same connectivity but differ in the spatial arrangement of atoms. This includes various forms such as cis-trans isomerism, where isomers differ in their spatial orientation around a double bond or a ring structure, but their connectivity remains unchanged.

Geometric isomerism is a specific category under stereoisomerism, primarily concerned with the different spatial arrangements due to restricted rotation (like around double bonds or within rings). While this is a type of stereoisomerism, it does not pertain directly to differences in connectivity.

Functional isomerism is a subset of structural isomerism where compounds with the same molecular formula differ in the functional groups present. For instance, alcohols and ethers can have the same formula (C2H6O) but display different functional properties due to the variations in the connectivity of hydrogen and oxygen atoms.

Thus, the term structural isomerism