The attraction between the partial negative charge at one end of a water molecule (on the oxygen atom) and the partial positive charge at the hydrogen end of another water molecule is called a hydrogen bond. This hydrogen bonding occurs because water is a polar molecule: oxygen is more electronegative than hydrogen, causing an uneven sharing of electrons that results in a partial negative charge on oxygen and a partial positive charge on hydrogen. When these molecules come close, the positively charged hydrogen atom of one molecule is attracted to the negatively charged oxygen atom of another, forming a hydrogen bond
. Hydrogen bonds are weaker than covalent bonds but are crucial for many of water's unique properties, such as its high surface tension, cohesion, and solvent abilities
