The bonded tableau unitary group approach (BTUGA) is used to calculate and analyze the structure of H2O, also the interactions between two bonding electron pairs, a bonding and a lone pairs as well as between two lone pairs are quant. discussed by using the bonded functions approaches. The results show that the electron d. centers of the two hybrid orbital in th oxygen atom which form bonds with 1s orbitals of the hydrogen atoms deviate from O-H bond axes. In fact, the oxygen atom bonds two hydrogen atoms with its p orbitals.

Key words: MOLECULAR ORBITAL THEORY, FUNCTION, ELECTRON PAIRS, CORRELATION ENERGY