Question

The edge length of the NaCl unit cell is if radius of $N{a}^{+}$ is 97 pm and radius of it is 181 pm :

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

Answer 1

The correct option is A 556 pm

for NaCl type structure
$2(r_{-}+r_{+})=a$
$2(97+181)=a$
$\therefore a=2\times 278pm$
$\therefore a=556pm$
a is edge length