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Why is water a polar molecule?

In this video, we'll explain simply why a water molecule is polar and it also has a bent shape.
Oxygen combines with 2 hydrogens in order to make 1 water molecule.

A water molecule, on the whole, is neutral. However, the electrons are not distributed evenly across the surface of the molecule and this causes the ends to be slightly charged.

Water has a lone pair of electrons

    • When oxygen bonds with hydrogen, oxygen attract electrons more strongly than hydrogen because of the higher electronegativity charge. The charge is caused by the protons - the positively charged protons in the nucleus attract the negatively charged electrons.
    • Because of the stronger electronegative force in oxygen (oxygen has more protons than hydrogen), it causes the bonding pair of electrons to be held closer to the oxygen atom.
    • The electrons are not equally shared and this results in oxygen having a slightly negative charge while the hydrogen has a slightly positive charge.
    • This separation of charges is termed dipole moment.

Water has a bent shape

Water is a bent shape

    • The lone pair of electrons in the oxygen atom are not bonded to any atoms so they are free to repulse each other.
    • These repulsive forces act to push the hydrogen atoms closer together and create a compression angle of 104º.
    • Due to the special bent shape of the water molecule, this causes the water molecules to build crystal structure when water freezes.
    • Hence water has a unique nature of expanding when it freezes.
    • Please remember this is a 2D model and it does not represent how electrons are spread over a "volume" of space. The shape of the molecule is described as a "bent shape" but the electrons are tetrahedrally arranged.