Learn

84

Dipole Attraction

Expert
1
m

Dipole - Dipole forces are usually found between molecules that have a difference in electronegativity so the electrons are unevenly distributed meaning that the molecule is polar. Due to its polarity this means a weak dipole forms which forms a weak intermolecular attraction to the molecule next to it.

Molecules that are polar however have slightly stronger forces of attraction. These molecules unlike London dispersion forces have permanent dipoles as they are polar molecules. These molecules have different electronegativities meaning they have a permanent poles of positive and negative. These positive dipoles can be shown by small delta + and delta - charges on a molecule. This means the electrons are more attracted to one atom in the bond than another and the electron distribution is uneven.


The strength of these interactions will depend on how big the dipole is and also how they are orientated and also the size of the atoms with larger molecules and compounds having larger dipoles. These dipoles being permanent compared to the temporary and instantaneous dipoles of London dispersion forces means they are stronger and require more energy to cause them to break. This means substances in general that have dipole dipole interactions which are stronger. For example, a molecule of hydrogen chloride where hydrogen has an electronegativity of 2.2 and chlorine has a value of 3.16 has a difference of nearly 1.0 this means that the dipole is permanent as the chlorine will have more of the electron density giving it a permanent negative dipole and hydrogen a permanent positive dipole. This means that hydrochloric acid has a boiling point of 108.6 degrees and is a liquid at room temperature compared to chlorine which has only london dispersion forces and a boiling point of -34 degrees meaning it is a gas at room temperature.



Terms in section
Electronegativity

Electronegativity is the ability of an atom to attract electrons in its bond determined by the nuclear charge, number of protons and the number of shells.

Permenant pole

A permanent pole is the result of a difference in electronegativites over 0.5 on the pauling scale so the distribution of electrons on a molecule are uneven

Delta

Delta is the symbol used to show a small partial charge on an atom which is the result of an uneven distribution of electrons

Instantaneous dipole

An instantaneous dipole is the term given to a molecule when a dipole of uneven charges is created very quickly and randomly in a molecule

Orientated

Orientated is a. term used to describe the direction in which a. molecule faces

Previous

London Dispersion Forces

1
m
Next

Hydrogen Bonding

1
m