What are Polar Compounds?
Polar compounds are chemical compounds that are held together by polar covalent bonds. The term ‘polar compound’ can be defined as a chemical species which consists of two or more atoms that are held together by covalent bonds that are polar in nature due to the unequal sharing of electrons. When two atoms are bound together via a covalent bond, the differences in the electronegativities of the bonded atoms may cause the bond pair of electrons to shift closer to the more electronegative atom. This results in the accumulation of a partial positive charge at the location of the more electropositive atom and the accumulation of a partial negative charge at the location of the more electronegative atom. Polar compounds are chemical compounds that are held together by such bonds.
It is important to note that polar compounds are not the same as ionic compounds. Ionic compounds are held together by ionic bonds that arise due to electrostatic forces between ions. In such cases, one of the atoms loses an electron to form a cation and another atom gains an atom to form an anion. In polar compounds, the electron pair is shared by two chemical species. However, the electron pair is shared in an unequal manner owing to the differences in the electronegativities of the two chemically bonded species.
Examples of Polar Compounds
Water is a polar compound because the covalent bonds between hydrogen and oxygen in the water molecule are polar in nature. The bond polarity in the hydrogen-oxygen bond arises due to the differences in the electronegativities of hydrogen and oxygen. Since oxygen is more electronegative than hydrogen, it pulls the bond pair of electrons closer to itself. This causes the oxygen atom to develop a partial negative charge and the hydrogen atom to develop a partial positive charge.
Hydrogen Fluoride (HF)
Hydrogen fluoride is a polar compound because the covalent bond between hydrogen and fluorine in this compound has a polar nature. Since fluorine is much more electronegative than hydrogen, it pulls the bond pair of electrons closer to itself, developing a partial negative charge in the process. On the other hand, the hydrogen atom develops a partial positive charge (since the bond pair of electrons is placed quite far away from the nucleus of the hydrogen atom).
The ethanol molecule features a polar covalent bond between the terminal carbon and the hydroxyl group. This carbon-oxygen bond is polar in nature because oxygen is more electronegative than carbon, causing it to shift the bond pair of electrons closer to itself and obtaining a partial negative charge in the process. The carbon atom gains a partial positive charge since the electron pair is placed relatively far away from its nucleus.
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