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dipole dipole forces

i try to look answer on internet but cant find answer
just try to find that
did temporary dipole dipole forces increases as no of electron increases
eg halogen boiling point increases because the number of electrons increases down the group so more vdw .......blah blah ......

but there is also temporary dipole dipole forces . did these forces increases when number of electrons increases.
I don't think so. Van der Waals increase with the number of electrons. The dipole-dipole is affected by electronegatively.
Reply 2
Original post by OwlOfFire
I don't think so. Van der Waals increase with the number of electrons. The dipole-dipole is affected by electronegatively.


so you are saying that dipole forces decrease down the group
Original post by OwlOfFire
I don't think so. Van der Waals increase with the number of electrons. The dipole-dipole is affected by electronegatively.


nah the term "(induced) dipole-dipole is a substitute for Van der Waals forces.

if you started ocr chem in 2015 after the reform you're not allowed to refer to them as van der waals but rather induced dipole-dipole forces, but they're the same thing.
not sure about other exam boards.
Original post by Qer
so you are saying that dipole forces decrease down the group


yeah induced dipole-dipole forces increase down a group since down a group the number of electrons increases.
more electrons/bigger species=stronger induced dipole dipole forces.
Reply 5
Original post by hamzakalinle
yeah induced dipole-dipole forces increase down a group since down a group the number of electrons increases.
more electrons/bigger species=stronger induced dipole dipole forces.


thanks
Reply 6
Original post by hamzakalinle
if you started ocr chem in 2015 after the reform you're not allowed to refer to them as van der waals but rather induced dipole-dipole forces, but they're the same thing.


They are not the same thing, which is why OCR no longer accept VdW for IDD.

VdW = both IDD and PDD.

Pre the spec change they incorrectly used VdW as an alternative to IDID only (as they used to call it), what they have done is correct that mistake.

But, whatever you do, don't just write the initialised forms of the names, unless you've written them out in full at some point.
Reply 7
doing aqa
Reply 8
Original post by Pigster
They are not the same thing, which is why OCR no longer accept VdW for IDD.

VdW = both IDD and PDD.

Pre the spec change they incorrectly used VdW as an alternative to IDID only (as they used to call it), what they have done is correct that mistake.

But, whatever you do, don't just write the initialised forms of the names, unless you've written them out in full at some point.


so i have to write that no of electrons increases due to which VDW and induced dipole dipole forces increase..................................
In AQA (reformed) we used "van der Waals" and "permanent dipole-permanent dipole".

Instantaneous Induced Dipole= van der Walls

(That is what we learnt anyway :smile: )
Reply 10
Original post by OwlOfFire
In AQA (reformed) we used "van der Waals" and "permanent dipole-permanent dipole".

Instantaneous Induced Dipole= van der Walls

(That is what we learnt anyway :smile: )


right
Original post by Qer
so i have to write that no of electrons increases due to which VDW and induced dipole dipole forces increase..................................


For the new OCR A, it is best to just avoid using the term VdW.

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