Advanced Placement (AP) Chemistry Practice Exam 2025 - Free AP Chemistry Practice Questions and Study Guide

Single bonds are characterized by the presence of one sigma bond, which is formed by the head-on overlapping of atomic orbitals. This overlap allows for a shared pair of electrons between the two bonded atoms, confirming that a single bond does indeed consist of one sigma bond and one electron pair.

In this context, it’s essential to understand that a sigma bond is the primary bond in single bond formation, providing the strongest attraction between the two nuclei. The mention of an electron pair is important because the definition of a covalent bond fundamentally revolves around the sharing of electron pairs.

The other options don't accurately reflect the nature of single bonds. For instance, the suggestion that single bonds consist of two sigma bonds would apply to a double bond scenario, which involves one sigma bond and one pi bond, not a single bond. Hence, the structure and characteristics of single bonds focus primarily on the singular sigma bond and the sharing of one electron pair, making the choice that highlights these aspects the most precise.