Which statement best explains how electrons form a covalent bond in a molecule?

B. A pair of electrons belongs to two atoms at the same time

Explanation:

Covalent bonding occurs between two unstable elements through sharing of pair of electrons. During bonding, two elements combines and shares a pair of electron to form a molecule. This electron completes both elements outermost shell and thereby forming a compound. Example of a compound that forms covalent bonding is sodium chloride (NaCl).

Sodium which is a group1 element possesses just one electron in its outer shell while chlorine, a group 7 element possess 7 valence electrons in its outermost shell making them unstable. Sodium acts as a donor by donating its lone pair of electron to chlorine thereby becoming a positively charged element while chlorine accepts this line pair of electron to completes its outermost shell making it stable and becoming negatively charged particle (being the acceptor). This bonding between this atoms if different elements is what is called covalent bonding.

covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms

the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration.