In molecular structures, what does the presence of lone pairs typically result in?

The presence of lone pairs in molecular structures indeed results in changes to molecular geometry. Lone pairs, being electron-rich regions that are not shared between atoms, exert repulsive forces on neighboring bonding pairs. This repulsion alters the arrangement of atoms around the central atom.

For example, in a molecule like ammonia (NH3), the central nitrogen atom has one lone pair and three hydrogen atoms. The lone pair pushes down on the molecular geometry, creating a trigonal pyramidal shape rather than a flat structure. This alteration is consistent across many molecules and impacts angles between bonds, leading to geometries such as bent, pyramidal, or others depending on the number of bonding pairs versus lone pairs.

The other options don't adequately reflect the influence of lone pairs. While they can impact boiling points or bond formation indirectly, the direct and most observable effect of lone pairs is their influence on the shape and geometry of the molecule.