Water molecule is not linear although it is of the type AB2.Please explain.Chemistry

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ndnordic | High School Teacher | (Level 2) Associate Educator

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A water molecule is not linear because of the electron structure of the oxygen atoms in the water molecules.  Oxygen has 6 valence electrons in the second energy level. Its configuration is 1s2 2s2 2p4.  Because of this configuration oxygen has two electron pairs and two single valence electrons.  When oxygen combines with hydrogen to form water each of the single electron pairs combines with an electron from hydrogen to form a single bond. However, the electron pairs take up a relatively large amount of space around the oxygen atom and because of the natural repulsion between the electron pairs and the electrons in the O-H bonds, these bonds bend to form an angle of about 107 degrees rather than being linear as expected.