given the distribution of charges shown in this water molecule, why is it called polar?
Given the distribution of charges shown in this water molecule, why is it called polar?
Answer:
A water molecule is called polar due to the uneven distribution of electrical charges within the molecule, which arises from its specific molecular structure and the difference in electronegativity between its atoms.
Solution By Steps:
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Molecular Structure and Shape:
- Water (H_2O) has a bent molecular shape due to the two hydrogen atoms bonded to a single oxygen atom. This shape is based on the “bent” configuration formed by the two hydrogen-oxygen bonds and the non-bonded electron pairs on the oxygen atom.
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Electronegativity Differences:
- Oxygen is more electronegative than hydrogen, meaning it has a stronger tendency to attract electrons towards itself. This difference in electronegativity causes the electrons in the O-H bonds to be more concentrated around the oxygen atom.
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Partial Charges:
- As a result, the oxygen end of the molecule attains a partial negative charge (\delta^-), and the hydrogen ends attain partial positive charges (\delta^+). This separation of charges creates a dipole moment.
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Overall Molecular Polarity:
- Due to the molecule’s bent shape, the dipole moments do not cancel each other out but instead add up to create a net dipole moment. This gives water its polar characteristic, with one end being more negative and the opposite end more positive.
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Consequences of Polarity:
- The polarity of water leads to hydrogen bonding, where the positively charged hydrogen ends attract the negatively charged ends of other polar molecules. This property accounts for water’s unique characteristics, such as high surface tension, capillarity, and its role as a universal solvent.
Thus, the polar nature of water is due to its bent shape and the difference in electronegativity between oxygen and hydrogen, resulting in a net dipole moment across the molecule.