The radii of Na ⁺ and Cl ⁻ ions are 95 pin and 181 pm respectively. The edge length of NaCl unit cell is

Step-by-step solution

NaCl forms fec structure. ( Diagonal length )²=( 2 a)²=2 (r⁺ )²+2 (r⁻ )² Where, a= edge length, r⁺ and r⁻ are radii of Na ⁺ and Cl ⁻ ions. a=2 [ (r⁺ )²+ (r⁻ )² ]=2(95+181)=2 276=552 pm