The asymmetry of the water molecule leads to a dipole moment in the symmetry plane pointed toward the more positive hydrogen atoms. The measured magnitude of this dipole moment is μ ⃗ = ∑i qi r ⃗ i
A dipole exists (for covalent bonds) when there is a separation of charge created when there is unequal sharing of the pair of electrons in the covalent bond. The net molecular dipole moment for water is 1.85 D. Because of the lone pair on oxygen, the structure of H2O is bent, which that the vectors representing the dipole moment of each bond do not cancel each other out. Hence, water is polar.