Posted by Amanda on Saturday, February 20, 2010 at 4:37pm.
I could work this problem if it had units. No units on density, none on radius (that could be pm, nm, what?).
Sorry about that - the density is 1.55 g/cm3 and the radius is 0.197 nm.
There are 4 atoms to the unit cell in a fcc.
(4*atomic mass /6.02 x 10^23) = mass of unit cell. You need the mass.
4*radius atom = a*21/2
Solve the last equation for a
volume of unit cell = a3
Then plug into mass = volume x density to calculate mass of unit cell. Plug mass into the top equation to calculate atomic mass.
By the way, I would not use the radius in pm. I would change that to cm first thing out of the cage; otherwise you must convert volume in pm3 to cc and that's a little more difficult and one more step to make an error. Same thing for your next post.
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