Final answer:
The presence or absence of lone pairs in a Lewis structure determines if a molecule's electron-pair geometry and molecular structure will be identical; they will be the same only if there are no lone pairs on the central atom. The feature of a Lewis structure that can be used to tell if a molecule's (or ion's) electron-pair geometry and molecular structure will be identical is (c) Lone pairs.
Step-by-step explanation:
The feature of a Lewis structure that can be used to tell if a molecule's (or ion's) electron-pair geometry and molecular structure will be identical is (c) Lone pairs. This is because the electron-pair geometry includes all domains of electron density, including bonding pairs and lone pairs, whereas molecular structure only considers the placement of the atoms themselves. The geometries will be the same when there are no lone electron pairs present on the central atom. When lone pairs are present, they will alter the electron-pair geometry, causing the molecular structure to potentially differ.
The feature of a Lewis structure that can be used to tell if a molecule's electron-pair geometry and molecular structure will be identical is lone pairs. Lone pairs are non-bonding pairs of electrons that influence the overall shape and geometry of a molecule. When there are no lone pairs present around the central atom, the electron-pair geometry and molecular structure will be identical. However, if there are lone pairs present on the central atom, the electron-pair geometry and molecular structure will be different.