What is the term for isomers with the same molecular formula but different spatial arrangements?

The term "stereoisomers" refers to isomers that have the same molecular formula but differ in the three-dimensional arrangement of their atoms in space. This group of isomers includes two main types: geometrical (cis/trans) isomers and optical isomers (enantiomers). Stereoisomers maintain the same connectivity of atoms but differ in their spatial orientations, which can lead to different chemical properties and reactivities.

For instance, consider a compound like butene, which can exist as cis-2-butene and trans-2-butene. Although they share the same molecular formula (C4H8), the different spatial arrangements of the double bond lead to distinct physical and chemical properties.

Structural isomers, on the other hand, have the same molecular formula but differ in the connectivity of their atoms, which is a different concept altogether. Geometric isomers are a subset of stereoisomers characterized specifically by the presence of restricted rotation, usually due to double bonds. Conformational isomers involve molecules that can rotate around single bonds to adopt different shapes or conformations without breaking any bonds, which again is distinct from the definition of stereoisomers. Thus, the term that best fits the description provided in the question is stereois