Nonpolar bonds result from equal electron sharing between atoms, forming nonpolar molecules without charge separation. Diatomic molecules, like oxygen, are common examples. A molecule can be nonpolar even if its atoms are connected via polar covalent bonds. Hydrophobic behavior in organic compounds, like lipids, is due to their nonpolarity. Carbon dioxide is a nonpolar molecule with polar bonds due to its symmetric structure.
A nonpolar bond is a covalent bond between atoms in which electrons are shared equally between the atoms. Equal sharing of electrons leads to the formation of a non-polar molecule that has no electric dipole moment or electric charge separation. Two identical atoms will form a non-polar bond because they have equal electronegativities.
A common example of a non-polar bond can be found in diatomic oxygen. Each oxygen atom has six electrons in its outer shell, and two more are needed to reach the stable noble gas configuration of eight electrons. In the oxygen molecule, atoms share a set of four electrons equally in double bonds, filling each atom’s need for two extra electrons. Each of these bonds would be considered a non-polar bond.
Nonpolar covalent bonds tend to be found in diatomic molecules, where two identical atoms are bonded together. These include iodine, hydrogen and nitrogen. The overall polarity of a molecule should not be confused with the polarity of its bonds. It is possible for a molecule to be nonpolar as a whole, even when its atoms are not connected via a nonpolar bond. This occurs when polar covalent bonds cancel each other’s charge due to the molecular structure.
In methane, the carbon is bonded to hydrogen in slightly polar bonds, resulting in a somewhat unequal sharing of electrons. The tetrahedral structure of the molecule causes these charges to cancel, resulting in a non-polar molecule. Even though the atoms are not bonded through non-polar bonds, the molecule behaves in a non-polar way.
This global non-polar interaction between hydrogen and carbon atoms makes organic compounds hydrophobic, meaning they cannot interact with water to form hydrogen bonds. When interacting with polar molecules, water forms hydrogen bonds between its own positively charged hydrogen atoms and an electronegative atom of another molecule. Non-polar compounds cannot perform this interaction because they have no charge separation throughout their structure and therefore no sites to attract a charge.
Hydrophobic behavior can be observed in household products such as vegetable oil, which visibly separate from water. The non-polarity of hydrophobic substances is also an important factor in the functioning of living organisms. Lipids, found in cellular structures, prevent water from mixing with internal structures and separating fluids. As with other organic compounds, these molecules are made up of bonds that are nearly, but not quite, non-polar: their bonding structure causes their polarity to cancel out.
Carbon dioxide is another example of a non-polar molecule with polar bonds. The structure of this molecule is linear, with two oxygen atoms doubly bonded to a central carbon atom. These bonds are polar covalent, but because they are exactly symmetric, their charges cancel each other out, creating a nonpolar molecule.
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