What makes a water molecule polar?
A water molecule contains two hydrogen atoms covalently bonded to one oxygen atom. Since hydrogen and oxygen do not have the same electronegativity (oxygen: 3.5 and hydrogen 2.2), each hydrogen – oxygen bond is polar covalent, with hydrogen having a partial positive charge and oxygen having a partial negative charge. The shape of the molecule is bent, because both hydrogen atoms are closer to one side of the molecule, with oxygen being the other side of the molecule. Thus, the concentration of the positive charge (the hydrogen atoms) is on one side to the molecule, while the negative charge (oxygen) is concentrated on the other side of the molecule. This orientation makes a water molecule polar, because it has two oppositely charge poles.
If you think about the structure of an H2O molecule, it is a covalent compound, where the oxygen shares two electrons with two hydrogen atoms. The Hydrogen atoms only have one proton in their nucleus, and the oxygen atom has 16. Because of the greater nuclear charge of the Oxygen atom, the bonded electrons are more attracted to the oxygen atom. If you consider the electron arrangement of oxygen, it has 6 electrons in its outer shell. This means it has 4 electrons that are not bonding, and these repel the bonding electrons, pushing the hydrogens down, and giving water its characteristic non-linear shape. Hope this helps!
A molecule is polar when its electron cloud is asymmetrical in a particular dimension. The water molecule is made of two hydrogen atoms bound covalently to a central oxygen atom. Around the central oxygen atom, there are 2 bond electron pairs (from the covalent bonds with hydrogen), and two lone pairs, which aren’t bonded to another atom. Hence, we can use the Valance Shell Electron Pair Repulsion theory (VSEPR) to predict that the shape of the water molecule is bent, with an angle of 105°. The central oxygen atom is more electronegative compared to the two companion hydrogen atoms, hence it draws electrons to itself. As the molecule is bent, the electrons will be drawn towards the apex of the H-O-H “angle”, towards the oxygen atom. Thus, there is an asymmetry in the electron distribution in the water molecule. Due to this inherent asymmetry in electron distribution, the water molecule is polar. The oxygen atom is slightly negatively charged, and the hydrogen atoms are slightly positiv
