What are structural isomers?

Structural isomers are compounds that share the same molecular formula but differ in the way the atoms are arranged, leading to different structural configurations. This variation in arrangement can affect the chemical and physical properties of the compounds, even though they contain the same types and numbers of atoms.

For example, butane (C4H10) can exist in two structural forms: n-butane, which is a straight-chain alkane, and isobutane, which is a branched-chain version. These different structures result in distinct properties such as boiling points and reactivity.

The other options do not accurately describe structural isomers. Compounds with different empirical formulas reflect a different ratio of elements and are considered different compounds altogether. Identical compounds would not fit the definition of isomers, as they possess no difference in their structure. Lastly, compounds differing only in molecular weight implies a variation in the number of atoms or types of elements, which falls outside the definition of structural isomers.