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How does a covalent bond share electrons between atoms?

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Bohr model diagram of a hydrogen atom showing a green nucleus labeled H, a single electron orbit, and text with atomic mass 1.008 and electron configuration 1. — atom The Bohr model describes the structure of atoms, in this case hydrogen.

A covalent bond is a chemical linkage formed when two atoms share a pair of valence electrons. This interaction occurs primarily between nonmetal atoms, which lack the low ionization energy required for electron transfer.12

The fundamental mechanism of this bond involves the electrostatic attraction of the nuclei of both atoms for the same shared electron pair. By sharing these electrons, each atom can attain a more stable electronic configuration—often a closed-shell octet—which results in a lower total energy for the bonded system compared to the atoms when they are widely separated.21

While simple models describe this as atoms "tossing" electrons back and forth, quantum mechanics provides a more precise view: the shared electrons reside in the space between the two nuclei, where they are attracted to both centers simultaneously. If the atoms involved have different electronegativities, the shared pair may be drawn closer to one atom, creating a polar bond with partial electrical charges.1342