destroyer gchem #54

[siba]

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Hi guys! For choice (A): Kr will melt at a higher temperature than Ne due to stronger dispersion forces. The answer key says it's correct, but doesn't elaborate on the explanation.

I couldn't see the relationship between size and dispersion force. I thought the bigger size, the more loosely bound electrons around the nucleus, and easier to be broken off.

Could someone explain?

Thanks!

 

[klpennin]

Hi guys! For choice (A): Kr will melt at a higher temperature than Ne due to stronger dispersion forces. The answer key says it's correct, but doesn't elaborate on the explanation.

I couldn't see the relationship between size and dispersion force. I thought the bigger size, the more loosely bound electrons around the nucleus, and easier to be broken off.

Could someone explain?

Thanks!

I don't have the problem in front of me, but the bigger a molecule is, the more Surface area it will have and it is more polarizable. So, the more polarizeable it is, more dispersion forces will be present.

Note: Dispersion forces are intermolecular forces that occur between molecules of a substance(s)

 

[siba]

I don't have the problem in front of me, but the bigger a molecule is, the more Surface area it will have and it is more polarizable. So, the more polarizeable it is, more dispersion forces will be present.

Note: Dispersion forces are intermolecular forces that occur between molecules of a substance(s)

Thanks for your reply! But I still couldn't see how having bigger surface area makes the molecule more polarizable.

I think the bigger it is, and larger electron cloud it has, and the looser it gets.

 

[mistero]

You are right that in terms of the intramolecular bond, it is weaker bc the electrons are more loosely held, but the intermolecular dispersion forces are greater bc of the greater surface area available for one molecule to interact with another.

 

[siba]

THANK You!

 

[Tina324]

great q.

ok so just to clarify...
Kr has a larger radius (larger electron cloud), so BY ITSELF it is less stable and can lose e's easier than Ne can.
BUT since Kr IS BIGGER it has a larger surface area and when bonding to OTHER Kr's, it is more stable than NE's bonding to other NE's because there is more area on Kr for bonding to occur with?

please let me know if it sounds like I know what I am talkin about hehe