How does electron sharing occur in covalent bonds?

Electron sharing in covalent bonds occurs when atoms share pairs of electrons to achieve a stable electron configuration.

In a covalent bond, two atoms come together to share one or more pairs of electrons. This sharing allows each atom to reach a stable electron configuration, typically that of a noble gas. The shared electrons are counted as part of the electron configuration of both atoms involved in the bond, which is why they can help both atoms achieve stability.

The process begins when two atoms come close enough for their outermost (valence) electron shells to overlap. This overlap allows the electrons to move in an area around both atomic nuclei, effectively 'belonging' to both atoms. This is different from an ionic bond, where one atom completely transfers one or more electrons to the other atom.

The number of covalent bonds an atom can form is usually determined by the number of additional electrons needed to reach a stable configuration. For example, oxygen needs two more electrons to reach the stable configuration of neon, so it can form two covalent bonds. Hydrogen, on the other hand, needs only one more electron to reach the stable configuration of helium, so it can form one covalent bond.

The shared electron pair is often referred to as a 'bonding pair'. In addition to these, there may also be 'non-bonding pairs' or 'lone pairs' of electrons that are not shared. These can influence the shape of the molecule and its reactivity.

In summary, electron sharing in covalent bonds is a way for atoms to achieve a stable electron configuration by sharing their valence electrons. This process involves the overlap of atomic orbitals, allowing electrons to be shared between atoms.