Question

If the radius of $N{a}^{+}$ is $97$ pm and radius of $C{l}^{-}$ is $181$ pm, the edge length (in pm) of the NaCl unit cell will be :

• A. $556$
• B. $278$
• C. $139$
• D. $120$

Answer 1

The correct option is A $556$

For NaCl, edge length $=a=2\left(r_{+}{+r}_{-}\right)$

$\therefore a=2(97+181)=556$ pm

Option A is correct.