A face centered cubic cell has an edge length of 495 pm. What is that atomic radius?

r = ¼a√2

Explanation:

For a face centered cubic cell, which we call FCC, the atoms at the face diagonals touch each other.

Now, If we denote the edge length of cube to be "a" and the radius of the atom is denoted as "r", as seen in the attached FCC cell:

(√2)a = 4r

Divide both sides by 4 to get;

r = ¼a√2