In water (H2O), each hydrogen atom does not form a double bond with oxygen, despite two electrons being shared. This is because the oxygen atom can satisfy its valence shell by forming two single covalent bonds rather than a double bond.
In a water molecule, oxygen has six valence electrons, and it needs two more electrons to complete its octet (eight valence electrons) and achieve a stable configuration. Each hydrogen atom contributes one electron, forming two single covalent bonds with oxygen. This sharing of electrons allows each hydrogen atom to fulfill its duet (two valence electrons) requirement, while oxygen achieves its octet.
The structure of water is often represented using a Lewis dot structure, where two dots represent a shared pair of electrons between oxygen and each hydrogen. The oxygen atom is then surrounded by eight electrons: six of its own and two shared with hydrogen. This arrangement satisfies the octet rule for oxygen, and each hydrogen atom has its valence shell complete with two electrons.
The resulting structure resembles an inverted "V," with oxygen at the vertex and the two hydrogen atoms bonded to it. This arrangement allows water molecules to form hydrogen bonds with each other, contributing to the unique properties of water, such as its high boiling point, surface tension, and solvent capabilities.