Q. If the distance between $Na^{+}$ and $CI^{-}$ ions in sodium chloride crystal is $x$ pm, the length of the edge of the unit cell is
A) $\frac{x}{2}pm$
B) $\frac{x}{4}pm$
C) 2$x$ pm
D) 4$x$ pm
Explanation
(c)
[image:5_image31.emf]
Or, $a = \ \frac{2d}{\sqrt{3}} = \ \frac{2\ \times \ 4.52}{\sqrt{3}} = 5.219\mathring{\mathrm{A}} = 522\ pm$
$\therefore a = 2x$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.