intermolecular bonds... Watch

mchammer
Badges: 1
Rep:
?
#1
Report Thread starter 9 years ago
#1
is this a decent explanation of intermolecular bond strength:


Larger atoms have more electrons. The electrons are also held in shells further from the nucleus. This means that lots of electrons can easily be moved, meaning that large atoms are highly polarisable. This then means that they induce large dipoles in surrounding atoms. The two large dipoles are then held together by relatively strong electrostatic attraction (in comparison to smaller atoms) in a relatively strong intermolecular bond....?
thanks
0
reply
Kaeroll
Badges: 0
Rep:
?
#2
Report 9 years ago
#2
It's along the right lines but I'd say it's somewhat inaccurate. When you say "intermolecular bond strength", judging by your description you mean van der Waals ("instantaneous dipole-induced dipole") forces?

What you say about polarisability is accurate enough, but perhaps a simplification. You overlook other forces such as permanent dipole forces and the like. However, my main concern is your description of van der Waals forces as "strong electrostatic attraction". It seems to overplay the strength of these interactions; I'd not even describe them as "bonds", given their fleeting nature.
0
reply
Lrilol
Badges: 1
Rep:
?
#3
Report 9 years ago
#3
Don't describe them as bonds, merely forces.

Also atom size isn't a big deal when talking about most molecular forces. I would focus more on molecular size/ polarity/ElectroNegativity.
0
reply
LearningMath
Badges: 13
Rep:
?
#4
Report 9 years ago
#4
(Original post by Lrilol)
Don't describe them as bonds, merely forces.

Also atom size isn't a big deal when talking about most molecular forces. I would focus more on molecular size/ polarity/ElectroNegativity.
Salters chemistry specifically describes them as bonds not forces.

Van der walls forces is an all inclusive term for p-p dipoles, p-i dipoles, and i-i dipoles.
0
reply
Lrilol
Badges: 1
Rep:
?
#5
Report 9 years ago
#5
Well it's completely different from that on AQA I can tell you > <
0
reply
Kaeroll
Badges: 0
Rep:
?
#6
Report 9 years ago
#6
(Original post by LearningMath)
Van der walls forces is an all inclusive term for p-p dipoles, p-i dipoles, and i-i dipoles.
Right you are. I meant London forces. Having a thick day today.
0
reply
rikeshpatel92
Badges: 0
#7
Report 9 years ago
#7
When talking about intermolecular forces you are usually talking about either:
1.) Instantaneous dipole-induced dipole forces
2.) Permanent dipole-dipole forces
3.) Hydrogen "bonding"

1.) Instantaneous dipole-induced dipole forces are caused simply by the movement of electrons in atoms and molecules. At any one moment, the electrons in an atom are likely to be more on one side than the other. At this moment you get a dipole (a difference in charge between two atoms). This dipole then INDUCES another dipole in the opposite direction on another atom. The two dipoles are attracted to each other. In this way, all atoms and molecules are attracted to each other.

2.) Permanent dipole-dipole forces are caused by attraction between delta+ and delta- dipoles on an atom caused by a polar bond.

3.) Hydrogen bonding only happens when hydrogen is covalently bonded to either Fluorine, Nitrogen or Oxygen. They are so electronegative that they draw the bonding electrons away from the hydrogen. The bond is so polarised and the hydrogen has such a high charge density because it's so small that it forms hydrogen "bonds" with lone pairs of electrons on Fluorine/Nitrogen/Oxygen atoms in other molecules.

The main thing you need to know is that intermolecular forces are MUCH weaker that covalent/ionic/metallic bonds. Also a tip: When you talk about [1] (Instantaneous dipole-induced dipole forces) call them London forces and not Van der Waals forces cos' technically you can call all three Van der Waals forces.

Source: Edexcel AS Chemistry Revision
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Cranfield University
    Cranfield Forensic MSc Programme Open Day Postgraduate
    Thu, 25 Apr '19
  • University of the Arts London
    Open day: MA Footwear and MA Fashion Artefact Postgraduate
    Thu, 25 Apr '19
  • Cardiff Metropolitan University
    Undergraduate Open Day - Llandaff Campus Undergraduate
    Sat, 27 Apr '19

Have you registered to vote?

Yes! (446)
37.93%
No - but I will (88)
7.48%
No - I don't want to (80)
6.8%
No - I can't vote (<18, not in UK, etc) (562)
47.79%

Watched Threads

View All