london dispersion forces

[705340227]

How do you determine which molecules only experience london dispeserion forces? There was a question on the homework about this and I couldn't figure out how to tell.

[Samuel Flores 1E]

Hello! We know that all intermolecular attractions contain London forces. However, only nonpolar molecules will solely experience only London forces. This is because non-polar bonds would not experience dipole-dipole attraction or hydrogen bonding. So, to check if a molecule only has London forces, you must confirm that this molecule is nonpolar.

Hope this helps!

[Crystal Yu 1D]

Firstly, all molecules will experience London Dispersion Forces due to the temporary, induced dipoles caused by the changing electron density in a molecule. Large molecules will have greater London Dispersion Forces because they have more electrons and thus their induced dipoles will be stronger.

The real question here is how can you tell if a molecule has forces other than London Dispersion Forces. If the molecule does, then you can rule it out as an answer because it does not have ONLY London Dispersion Forces. There are two main other forces you will want to check for: 1. dipole-dipole and 2. hydrogen bonding.

1. Dipole-Dipole
I recommend sketching out a Lewis structure to determine whether or not the molecule is polar. You can compare the electronegativity of the atoms in the molecule to determine the dipole for each bond. Then, use this information to see if there is a net dipole. (Molecular structure is important to help you determine the direction of the net dipole.) If there is, then the molecule is polar and will have dipole-dipole attractions in addition to London Dispersion forces.

2. Hydrogen Bonding
H Bonds occur between a positive dipole H and a negative dipole F, O, or N. If this applies to the molecule, then it will have hydrogen bonding in addition to London Dispersion Forces.

I hope this helps! :)

[AnnaNovoselov1G]

All molecules exhibit London dispersion forces, but nonpolar molecules are the only ones with only London Dispersion Forces because they don't have any permanent dipoles (since the atoms have equal electronegativities).
For instance, Cl2 molecules would have LDFs between them. Temporary uneven electrons distributions will cause the atoms to form momentary dipoles.

[Evie Li_1H]

all molecules experience london dispersion forces, but to find out if a molecule experiences ONLY london forces is to look at polarity. this requires you to know about the elements' electronegativity and the molecules' overall geometry. for example, in the sapling it gave you CH3F, C2H6, NF3, I2, and BF3. Since I2 is made up of only one element, that one automatically only experiences london forces. BF3 has differences in electronegativity for B and F, but the shape (trigonal planar) makes the molecule nonpolar so it only experiences london dispersion. For C2H6, there is no difference in electronegativity for C and H, so the molecule is nonpolar and only experiences london dispersion. For CH3F and NF3, F and C and F and N both have differences in electronegativity and both geometries are polar shapes, so both molecules are able to experience forces other than London dispersion.

hope this helped a little :)

[Heidi Buri 2I]

Hi! All molecules experience London dispersion forces. Some molecules have larger or smaller London dispersion forces depending on the size. To determine if the molecules have more than just London dispersion focus, you must look at the other properties of the molecules and the atoms bonded to make the molecules. For example, if the molecule has a fluorine,oxygen, or nitrogen covalently bonded to a hydrogen, the molecule could have hydrogen bonding along with London dispersion focus.