When a molecule is polar, it means there is an uneven distribution of electric charge within the molecule. One side of the molecule has a partial positive charge, while the opposite side has a partial negative charge, creating a dipole. This occurs because the atoms in the molecule have different electronegativities, causing electrons to be shared unequally. Additionally, the molecular geometry must be such that these charge differences do not cancel out. For example, water (H2O) is polar because the oxygen atom pulls electrons more strongly than the hydrogen atoms, resulting in a partial negative charge near the oxygen and a partial positive charge near the hydrogens, and the bent shape prevents the charges from canceling out.
Key Points:
- Polar molecules have regions of partial positive and partial negative charge (dipole).
- Polarity depends on differences in electronegativity and the shape of the molecule.
- Polar molecules tend to interact through dipole-dipole forces and may have unique properties like dissolving other polar substances.
Thus, polarity describes a molecule with an asymmetric charge distribution giving it distinct positive and negative poles.
