Q. Sodium metal crystallises at room temperature in a body centred cubic lattice with a cell edge $a = 4.29\ \mathring{\mathrm{A}}.$ The radius of sodium atom is
A) 1.40
B) 2.65
C) 1.85
D) 2.15
Explanation
(c)
For a body centred cubic lattice radius, $(r)$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{\sqrt{3}}{4}a = 0.433a$
Therefore, radius of $Na^{+} = 0.433 \times 4.29 = 1.8575$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.