Caption：A water molecule can form up to four hydrogen bonds simultaneously. The oxygen atom of a water molecule is the hydrogen bond acceptor for two hydrogen atoms . Each O-H group serves as a hydrogen bond donor.
Notes:The tetrahedral structure of the water hydrogen bonds is a consequence of the sp3 hybridization of the oxygen's electrons. The two hydrogen bonds between the oxygen and the hydrogen atoms on another water molecule utilze the two partly-negative pairs of unbonded electrons on oxygen.