posted by Fred .
Platinum has a face-centered cubic crystal structure and a density of 21.5 g/cm3. What is the radius of the platinum atom?
The fcc has 4 atoms/unit cell.
Mass of 1 atom Pt = 195.08/6.02 x 10^23.
Mass of unit cell is 4 times that.
Then m = volume x density. You know density and mass, calculate volume of unit cell. From volume = a3 you can calculate a (the length of the side).
For a fcc unit cell, 4*radius = a*21/2. You know a and that allows you to calculate radius.
Post your work if you get stuck.
is not 98. try 139