Intermolecular Forces Definition | Types |

INTERMOLECULAR FORCES.

Have y'all always wondered why some compounds boil at relatively depression temperatures land some boil at high temperatures? Why some melt at depression temperatures land some melt at high temperatures? Why some be every bit a gas at room temperature land some every bit liquid or solid? To hold out able to response those questions nosotros must sympathize the concept of intermolecular forces.

Intermolecular forces are forces that bind molecules together inward a compound. Different intermolecular forces vary inward their strength but they are mostly weaker than intramolecular chemic bonds (ionic, covalent or metallic element bonds). Thus, when a chemical compound changes from i stage to another, its molecules stay intent. Although intermolecular forces are much weaker than the major chemic bonds, their beingness cannot hold out overlooked because they are related largely to the physical properties of a compound, such every bit its boiling point, melting point, e.t.c. For a liquid to boil or a venture to melt, it must absorb liberate energy that tin overcome its intermolecular forces. Thus, a liquid or venture having stronger intermolecular forces tends to boil or melt at high temperatures. Also, the divergence inward the phases of affair is how tightly its molecules are held together which is a component division of its intermolecular forces.

TYPES OF INTERMOLECULAR FORCES.

There are iii types of intermolecular forces, all these types of intermolecular forces are electrostatic in nature i.e involving attraction betwixt positive in addition to negative species.

Dipole-dipole force.

When atoms of unlike electronegativity bond together to shape a molecule, the to a greater extent than electronegative one tends to describe the electrons inward the bonds towards itself, making it instruct a partial negative charge and the other to instruct a partial positive charge. Thus, creating a permanent dipole moment, such molecules are arranged inward such a agency that the partially positive cease of i molecule is attracted to the partially negative cease of the neighboring molecule. This type of attraction is called dipole-dipole attraction. An example of this forcefulness tin hold out observed betwixt the molecules of HCl where the partially negative Cl atom of i molecule is electrostatically attracted to the partially H of some other molecule.

Dispersion Force.

If intermolecular forces are said to hold out electrostatic inward nature, does that infer that neutral in addition to nonpolar compounds practice non convey intermolecular forces? If yes, how in addition to then practice nosotros concern human relationship for the liquefaction of nonpolar gases?

In 1930, Fritz London observed that the displace of electrons inward an atom or molecule tin practice a momentary dipole moment. Since electrons to a greater extent than or less the nucleus are non static but are inward continuous motion, in that location comes a fourth dimension when all the elections are clouded on i side of the nucleus. At that instant, the atom or molecule has an instantaneous dipole moment, this momentary dipole moment induces an instantaneous dipole instant on the neighboring molecule causing them to hold out attracted to each other, this type of attraction is known every bit dispersion forces.

Dispersion forces be betwixt nonpolar hydrocarbons.

Hydrogen bonding.

Hydrogen bonding is the attraction betwixt the partially positive hydrogen-bonded to a strongly electronegative atom similar N, O or F in addition to the lonely twain of electrons on its neighboring electronegative atom. The presence of the hydrogen bonding inward NH3 H2O in addition to HF is the argue for their odd high boiling points compare to other covalent hydrides.

A hydrogen bond is sub-divided into

Intermolecular hydrogen bond i.e betwixt ii molecules e.g HF, H2O e.t.c

Intramolecular hydrogen bond i.e inside the same molecule e.g o-nitrophenol.

Author. Akowe Nasir Aija