Q. Copper crystallises in fcc with a unit cell length of 361 pm. What is the radius of copper atom?
A) 108 pm
B) 127 pm
C) 157 pm
D) 181 pm
Explanation
(b)
In fcc unit cell
$\ \ \ \ \ \sqrt{2a} = 4r\ \ \ \ \Rightarrow r = \frac{\sqrt{2}\ a}{4}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{\sqrt{2} \times 361}{4} = 127\ pm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.