Ar is a solid below -189 oc with a face-centered cubic array of atoms and a supposed density of 1.32 g/cm3. assuming that the atoms are spheres in contact along the face diagonal, what is the radius of a ar atom (in angstroms)? an angstrom = 10-10 m or 10-8 cm. hint, first find the length of an edge of the unit cell. (argon's actual density is 1.65 g/cm3.)

The radius the Argon atom in

Solution:

As per the question:

Density of the solid,

No. of atoms present in FCC lattice, Z = 4

Now,

Mass of Argon, m = 40 g/mol

Density of the unit cell is given by the formula:

                     (1)

where

a = edge length

= Avogadro's number

Now,

Now,

In FCC unit cell, the relation between the radius, R and the edge length, a is given by: