The structure of water molecule is very simple. A water molecule is made up of one oxygen atom and two hydrogen atoms. The hydrogen atoms are covalently bonded to the oxygen atom by sharing a pair of electrons. The oxygen atom has two unshared electron pairs that makes a total of 4 electron pairs present around the oxygen atom.

Of these 4 electron pairs of oxygen, 2 electron pairs are involved in the covalent bond with hydrogen and the two lone-pair electrons are present on the opposite side of the oxygen atom. This gives oxygen a negative charge and makes it an 'electronegative' atom. In other words, it is an 'electron-loving' atom. The two lone-pairs of electrons on the oxygen atom make the H-O-H bond angle at 104.5º. This angel is slightly less than the 109º28' of the tetrahedral angle. This makes the structure of water molecule an angular structure.