Van der Waals radius not applicable to most elements?

[HappyEngineer]

I was looking at the values for the Van der Waals radius on various elements in wikipedia and noticed that Molybdenum does not have one. I searched a bit and found this site
http://www.webelements.com/periodicity/van_der_waals_radius/
which lists the elements that have a Van der Waals radius. The non-purple ones apparently do not have one.

Why is that? I don't see anything in the definition of the Van der Waals radius on wikipedia which indicates that it doesn't apply to most types of elements.

 

[stewartcs]

I was looking at the values for the Van der Waals radius on various elements in wikipedia and noticed that Molybdenum does not have one. I searched a bit and found this site
http://www.webelements.com/periodicity/van_der_waals_radius/
which lists the elements that have a Van der Waals radius. The non-purple ones apparently do not have one.

Why is that? I don't see anything in the definition of the Van der Waals radius on wikipedia which indicates that it doesn't apply to most types of elements.

Perhaps it is due to the inability to measure the intermolecular distances (for whatever reason, e.g. structure). Not sure though.

CS

 

[HappyEngineer]

So you're saying that they're not filled in because it's difficult to measure?

 

[melior]

From my understanding the simplest way to get the Van der Waals radius is to calculate it using ab initio software. The elements that haven't been calculated then are either not widely used or are too big to have been implemented in the ab initio systems yet. Any element that can form a bond would have to have a Van der Waals radius.

 

[Enjolras1789]

Funny this question should come up, seeing as I happen to be researching it. The current standards in van de Waals radii come from the most cited paper in the Journal of Physical Chemistry, written by A. Bondi. They still represent the best general, all-purpose radii if one must write in distances and not calculate, even though it was written in 1964. Bondi used mostly x-ray crystallographic data for the purpose. People who have come up with different values do so from a variety of different perpsectives of what a good experiment is to analyze.

Maybe, if I am successful (probably not the way it is going right now...), the entire Periodic Table will be published!

 

[Primordial]

I noticed an article on wiki, under the Casimir Effect at short range distances, being analysed with the effect of Van der Waals' force. This may be of help to you.