A molecule that can exist in multiple structural forms due to different arrangements of atoms is called what?

A molecule that can exist in multiple structural forms due to different arrangements of atoms is referred to as an isomer. Isomers are compounds that have the same molecular formula but differ in the arrangement of atoms. This can occur through structural isomerism, where the connectivity of atoms is different, or stereoisomerism, where the spatial arrangement of atoms differs.

For instance, consider glucose and fructose; both have the formula C6H12O6 but are structured differently. This variation in structure can lead to distinct physical and chemical properties, making isomers important in chemistry and biology.

The other options do not fit the definition. Homologs typically refer to genes or proteins that share a common ancestry, equilaterals relate to geometry and shapes specifically with equal sides and angles, and polymers are large molecules made up of repeating subunits. None of these terms encompass the concept of varied structural forms of a single molecular entity as isomers do.