RE: Chemistry Question

[Glen.Vickers@ucm.com]

The problem with looking at atomic diameters in estimating the number of
Thorium atoms is that Thorium flouride would exist as a molecule.  You would
need to know the arrangement of Thorium in the crystalline structure.  You
would need to know whether the crystallin structure is face-centered-cubic
or body-centered-cubic, to have a chance at calculating how molecules/atoms
would occupy a surface area.  I would also think this method would be
subject to a high degree of error.  An estimation of the distance between
Thorium atoms in their spatial molecule orientation is certainly subject to
error and then you would be multiplying that estimate by 10^8 or so.  

I think the best approximations over the past couple of days deal with
calculating the volume of material and moles/volume.

glen
glen.vickers@ucm.com

	-----Original Message-----
	From:	steve hand [SMTP:hand@wam.umd.edu]
	Sent:	Wednesday, June 23, 1999 8:11 AM
	To:	Multiple recipients of list
	Subject:	Re: Chemistry Question

	Tad:

	    Atoms have diameters on the order of angstroms (A) (with a dot
over the top).  If you can look up the diamater of the thorium-fluoride then
you can calculate the number of atoms of thorium.  1A = 10E-10 meters.
Knowing your
	dimensions for the lens you can calculate the total on the face.
Thorium is listed as having a radius of 0.95 A.

	    Hope this helps a little.

	Steve Hand
	Radiation Safety
	University of Maryland

	Tad Blanchard wrote:

	> Hello All,
	>
	> If a glass lens is coated with 1000 Angstroms of Thorium-Fluoride,
how do we determine the total activity (picocuries?) of the Thorium in the
coating?
	>
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