The phrase "water is a polar molecule" refers to the distribution of electrical charge across the water molecule, which leads to a positive and a negative end, resulting in a dipole moment.
What Creates a Polar Molecule
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Electronegativity: The polarity of a molecule is largely determined by the electronegativity of the atoms involved. Electronegativity is the tendency of an atom to attract electrons towards itself when bonded to another atom. In water (H₂O), oxygen (O) is significantly more electronegative than hydrogen (H).
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Covalent Bonds: Water is formed by two covalent bonds between oxygen and hydrogen. In these bonds, oxygen pulls the shared electrons closer to itself due to its higher electronegativity. This unequal sharing of electrons causes a partial negative charge (δ-) to develop on the oxygen atom, while the hydrogen atoms develop partial positive charges (δ+).
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Molecular Geometry: The shape of the water molecule is also important in understanding its polarity. Water has a bent or V-shaped geometry due to the two lone pairs of electrons on the oxygen atom. This results in an angle of about 104.5 degrees between the hydrogen atoms. The bent shape enhances the separation of charges, contributing further to the overall dipole moment of the molecule.
Summary of Characteristics
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Dipole Moment: The difference in charge distribution between oxygen and hydrogen results in a dipole moment, where one end of the molecule (the oxygen side) is slightly negative, and the other end (the hydrogen sides) is slightly positive.
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Polarity: Because of these characteristics, water is able to interact with other polar molecules and ions, making it a very effective solvent, which is crucial for many biological and chemical processes.
In summary, water’s designation as a "polar molecule" stems from the unequal sharing of electrons between oxygen and hydrogen, leading to a charge separation that is magnified by its bent molecular shape, creating a dipole.
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