London dispersion forces

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Jaclyn Schwartz 1I
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London dispersion forces

Postby Jaclyn Schwartz 1I » Sun Nov 08, 2020 6:08 pm

Can someone explain what London dispersion forces are? And how to differentiate between how strong the forces are?

IreneGi2I
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Re: London dispersion forces

Postby IreneGi2I » Sun Nov 08, 2020 6:15 pm

London dispersion forces are the same as Van der Waals forces or dipole-induced dipole. It basically explains the 'temporary attractive force' in an atom in which electrons are located more on the one side of the atom by random and instant chance. Since one side of atom has more electrons instantaneously, it will have partial negative charge. And, the other side with less electrons will have partial positive charge. London dispersion forces are the weakest intermolecular force. Hope this helps!

Giselle Granda 3F
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Re: London dispersion forces

Postby Giselle Granda 3F » Sun Nov 08, 2020 6:19 pm

London dispersion forces are temporary attraction forces between the electrons of two adjacent atoms. This means they form temporary dipoles, and are therefore the weakest intermolecular force! This is also easier to occur when there are more electrons in an atom since they are farther from the nucleus and thus can move around more freely.

John Pham 3L
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Re: London dispersion forces

Postby John Pham 3L » Sun Nov 08, 2020 6:22 pm

To add on, we can determine the strength in London dispersion forces by looking at the atom's polarizability.
Polarizability refers to the ease at which the electron cloud can be distorted.

Atoms that are highly polarizable have stronger London dispersion forces than those less polarizable.
This means that atoms that are larger and have more electrons will have stronger London dispersion forces.

JoshMoore2B
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Re: London dispersion forces

Postby JoshMoore2B » Sun Nov 08, 2020 6:40 pm

Jaclyn Schwartz 2D wrote:Can someone explain what London dispersion forces are? And how to differentiate between how strong the forces are?


London dispersion forces are forces that exist, in essence, by chance. They occur because of the unpredictable movement of electrons. Due to the fact that the electrons move unpredictably, there are brief periods of time in which electrons "pile up" on one side of the atom.

For instance, if you think of hydrogen and its one electron, you can see that its electron can't be completely surrounding the hydrogen atom all the time. So, there are periods of time where it is on one side of the atom, and periods of time where it is on the other, so to speak. When it is on one side of the atom, the other side is "exposed" and so it has a positive charge, attracting nearby negative charges, and the side with the electron has a negative charge.

London dispersion forces are effectively what I just described, but on a bigger scale with more electrons. When many of the electrons in an atom with multiple electrons randomly end up on one side of an atom, there is a brief period of time in which the side without the electrons has a positive charge, and the side with the electrons has a negative charge.

Due to their rather short-lived nature as well as their lack of interaction between overall pretty weak electrostatic forces, London dispersion forces tend to be pretty weak, but get stronger as atoms gain more electrons and get more electronegative.

Yichen Fan 3A
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Re: London dispersion forces

Postby Yichen Fan 3A » Sun Nov 08, 2020 7:25 pm

I totally agree with all the explanations that have been posted, just to make things clearer: London dispersion force is caused by the temporary polarization of the electron in atoms, therefore the more electrons an atom has a stronger London dispersion force it will possess, which means that the bigger the size of an atom its London dispersion force will be stronger.

Ryan_Kien_1L
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Re: London dispersion forces

Postby Ryan_Kien_1L » Sun Nov 08, 2020 7:26 pm

London dispersion forces (aka Van Der Waal Forces) are the weakest force between molecules that happen when molecules become temporarily polarized as electrons move around.

Rohit Srinivas 2D
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Re: London dispersion forces

Postby Rohit Srinivas 2D » Sun Nov 08, 2020 7:30 pm

I believe most replies above have the definition of London dispersion forces. Here is the order of bond strengths from strongest to weakest
1. Ionic bonds
2. Covalent bonds
3. Dipole Dipole bonds
4. Van der Waals (London dispersion)

Jaden Joodi 3J
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Re: London dispersion forces

Postby Jaden Joodi 3J » Sun Nov 08, 2020 7:31 pm

From what I understand, London dispersion forces are when, through random chance, electrons end up being on one side of the compound more than the other. This causes one end of the compound to be more negative, while the other end is more positive.

Jaden Kwon 3C
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Re: London dispersion forces

Postby Jaden Kwon 3C » Sun Nov 08, 2020 10:52 pm

London dispersion forces occur when the electrons in atoms form temporary dipoles due to chance. This force is the weakest intermolecular force.

Ayesha Aslam-Mir 3C
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Re: London dispersion forces

Postby Ayesha Aslam-Mir 3C » Sun Nov 08, 2020 11:01 pm

Rohit Srinivas 1C wrote:I believe most replies above have the definition of London dispersion forces. Here is the order of bond strengths from strongest to weakest
1. Ionic bonds
2. Covalent bonds
3. Dipole Dipole bonds
4. Van der Waals (London dispersion)



Are London Disperson/Van der Waals considered a form of bond? Or are they just IMFs?

Eve Gross-Sable 1B
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Re: London dispersion forces

Postby Eve Gross-Sable 1B » Sun Nov 08, 2020 11:09 pm

Ayesha Aslam-Mir 2E wrote:
Rohit Srinivas 1C wrote:I believe most replies above have the definition of London dispersion forces. Here is the order of bond strengths from strongest to weakest
1. Ionic bonds
2. Covalent bonds
3. Dipole Dipole bonds
4. Van der Waals (London dispersion)



Are London Disperson/Van der Waals considered a form of bond? Or are they just IMFs?


I believe they are just an IMF because they are a "force" and do not technically involve bonding. I think it is probably just significant that they are the weakest of the forces/attractions that can occur between molecules and will always be weaker than an actual bond.

Melanie Krahn 1C
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Re: London dispersion forces

Postby Melanie Krahn 1C » Sun Nov 08, 2020 11:11 pm

When would it be necessary to know what London dispersion forces are and how to recognize them?


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