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

The correct answer is structural isomerism, which occurs when compounds have the same molecular formula but differ in how their atoms are connected to one another. This means that despite having the same total number of each type of atom, the arrangement of those atoms varies, leading to compounds that are distinct from one another in their chemical properties and structure.

Structural isomerism encompasses several subtypes, including functional isomerism, where the isomers may differ in the functional groups present, and chain isomerism, where the carbon skeleton may be arranged differently (straight-chain vs branched). Each of these variations results in different compounds despite having the same molecular formula.

In contrast, stereoisomerism refers to isomers that have the same connectivity of atoms but differ in the spatial arrangement of those atoms. This can include geometric isomerism, which involves constraints like double bonds or rings that prevent free rotation. Therefore, while those types of isomerism focus on spatial configurations, structural isomerism highlights the importance of connectivity among atoms. This distinction is crucial in understanding and predicting the behavior of different chemical compounds.