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chem a level help needed

Silicon tetrafluoride (SiF4) is a tetrahedral molecule.
Deduce the type of intermolecular forces in SiF4
Explain how this type of intermolecular force arises and why no other type of
intermolecular force exists in a sample of SiF4


I have the mark scheme so please don't just give me an answer, and please explain how to get to the fact that it's van der waal forces
Reply 1
Avatar for Interea
Interea
19
Well there are 3 types of intermolecular forces - Van der Waal's, permanent dipole-dipole and hydrogen bonding. You need to discount the other 2 - what causes permanent dipoles, and what atoms are required to be present for hydrogen bonding?
Reply 2
Avatar for Hj5673
Hj5673
13
The only intermolecular force it has is V.D.W and this is because:

- it doesn't have hydrogen bonding as there is no hydrogen in the molecule so this can't occur
- it also doesn't have dipole-dipole bonding as there is no atom which has a much greater electronegativity than the other so this doesn't occur
- this means V.D.W is the only intermolecular force left which it can be as this occurs in every molecule

- V.D.W forces arise when a temporary dipole forms in one of the molecules and this then causes an induced temporary dipole to form in the neighbouring molecule. This then causes an electrostatic attraction.
Reply 3
Avatar for Ciel_
Ciel_
OP
14
Original post by Hj5673
The only intermolecular force it has is V.D.W and this is because:

- it doesn't have hydrogen bonding as there is no hydrogen in the molecule so this can't occur
- it also doesn't have dipole-dipole bonding as there is no atom which has a much greater electronegativity than the other so this doesn't occur
- this means V.D.W is the only intermolecular force left which it can be as this occurs in every molecule

- V.D.W forces arise when a temporary dipole forms in one of the molecules and this then causes an induced temporary dipole to form in the neighbouring molecule. This then causes an electrostatic attraction.

This makes a lot of sense thank you so much :smile:
Reply 4
Avatar for Ciel_
Ciel_
OP
14
Original post by Interea
Well there are 3 types of intermolecular forces - Van der Waal's, permanent dipole-dipole and hydrogen bonding. You need to discount the other 2 - what causes permanent dipoles, and what atoms are required to be present for hydrogen bonding?

I understand it now thank you so much
Reply 5
Avatar for Pigster
Pigster
20
Original post by Ciel_
Silicon tetrafluoride (SiF4) is a tetrahedral molecule.
Deduce the type of intermolecular forces in SiF4
Explain how this type of intermolecular force arises and why no other type of
intermolecular force exists in a sample of SiF4


I have the mark scheme so please don't just give me an answer, and please explain how to get to the fact that it's van der waal forces

Which spec do you study? The advice given by t'others in this thread may cause you to lose marks.
Reply 6
Avatar for Ciel_
Ciel_
OP
14
Original post by Pigster
Which spec do you study? The advice given by t'others in this thread may cause you to lose marks.

AQA a level
Reply 7
Avatar for Pigster
Pigster
20
Original post by Ciel_
AQA a level

In that case, you're fine.
Reply 8
Avatar for Ðeggs
Ðeggs
22
SiF4 has no overall dipole as well

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