|
 |
|
|
|
|
In chemistry, polarity refers to the dipole-dipole intermolecular forces between the slightly positively-charged end of one molecule to the negative end of another or the same molecule. Molecular polarity is dependent on the difference in electronegativity between atoms in a compound and the asymmetry of the compound’s structure. For example, water is thought to be polar because of the unequal sharing of its electrons. However, methane is considered non-polar because the carbon shares the hydrogen atoms uniformly.
A commonly-used example of a polar compound is water (H2O). The electrons of water’s hydrogen atoms are strongly attracted to the oxygen atom, and are actually closer to oxygen’s nucleus than to the hydrogen nuclei; thus, water has a relatively strong negative charge in the middle (red shade), and a positive charge at the ends (blue shade).
Diagram showing the net effect of symmetrical polar bonds (direction of yellow arrows show the migration of electrons) within boron trifluoride cancelling out to give a net polarity of zero. δ- shows an increase in negative charge and δ+ shows an increase in positive charge.
Polarity of the hydrogen halide molecules, HX. From the top, HF, HCl, HBr and HI. Electronegativity decreases from F to I, thus polarity decreases from HF to HI
