dispersions forces =S (1 Viewer)

[atrocityx]

being revising lately and i dont get dispersion forces TT"
could someone explain dispersion forces T^T" .
?

thanks.

 

[Xcelz]

Dispersion Forces

• are very weak forces of attraction between molecules resulting from:

1. momentary dipoles occurring due to uneven electron distributions in neighbouring molecules as they approach one another
2. the weak residual attraction of the nuclei in one molecule for the electrons in a neighbouring molecule.

• The more electrons that are present in the molecule, the stronger the dispersion forces will be.
• Dispersion forces are the only type of intermolecular force operating between non-polar molecules.

if this doesn't help just say

 

[mtsmahia]

Dispersion Forces

• are very weak forces of attraction between molecules resulting from:

1. momentary dipoles occurring due to uneven electron distributions in neighbouring molecules as they approach one another
2. the weak residual attraction of the nuclei in one molecule for the electrons in a neighbouring molecule.

• The more electrons that are present in the molecule, the stronger the dispersion forces will be.
• Dispersion forces are the only type of intermolecular force operating between non-polar molecules.

if this doesn't help just say

^ correct..and also remember
all molecules contain dispersion forces (whether, polar or non-polar molecules)
and you would normally get them when dealing with Diatomic molecules and others where the electronegativity of the atoms are similar..

or another way of looking at it is- Draw the structural formula for the molecule. determine whether it is polar or non-polar (lack of symmetry means non-polar). Then...all non-polar molecules contain dispersion forces...eg C02, and the polar ones will be dipole dipole or hydrogen bonding.

I realised i was repeating what i was said in the first para but meh...

 

[zazzy1234]

being revising lately and i dont get dispersion forces TT"
could someone explain dispersion forces T^T" .
?

thanks.

weak attracktive forces caused by uneven distribution of elcetrons. (it's polar).

 

[kaz1]

weak attracktive forces caused by uneven distribution of elcetrons. (it's polar).

Isn't that dipole-dipole interaction?

From what I remember in year 11 dipole-dipole interaction and dispersion forces are two distinct forms of intermolecular bonding.

To the OP: In a nutshell dispersion forces is the electrostatic force between a negative electron attracted to the positive nucleus in another atom/molecule.

 

[Lukybear]

Yep. Dipole - Dipole is completely different from dispersion forces.

A polar molecule is formed when there is an PERMANENT uneven distribution of charges within a molecule. When this polar molecule forms a bond with another polar molecule, by definition, a dipole-dipole bond is formed. I.e. Hydrogen bonding between water molecules, where -delta charge of oxygen links with +delta charge of hydrogen, both of which is permanent.

This however is different to dispersion forces, which are also known as tempory dipole-dipole forces. These are formed due to CHANCED uneven distribution of electron clouds. (And i think it has something to do with quantum mechanis?) As so forth, as stated by Xcelz.

 

[FFC]

Dispersion Forces

• are very weak forces of attraction between molecules resulting from:

1. momentary dipoles occurring due to uneven electron distributions in neighbouring molecules as they approach one another
2. the weak residual attraction of the nuclei in one molecule for the electrons in a neighbouring molecule.

• The more electrons that are present in the molecule, the stronger the dispersion forces will be.
• Dispersion forces are the only type of intermolecular force operating between non-polar molecules.

if this doesn't help just say

correct, and linear molecules (eg. Butane) will have stronger dispersion forces than branched chain molecules (eg. methylpropane). Both butane and methylpropane are of the formula C4H10 (and thus same number of electrons), however butane will have the higher MP/BP due to its stronger dispersion forces.