Question

What is the distance between Na⁺ and Cl^- ions in NaCl crystal if its density is 2.165 g cm^-3 ? 

[Atomic Mass of Na = 23u, Cl = 35.5 u; Avogadro's number = 6.023 x 10²³]

Answer 1

We know that

2(r⁺ + r^-) = a,

where r⁺ and r^- are radius of sodium & chloride ions respectively.

(r⁺ + r^-)  is the inter ionic distance

.'. Distance between Na⁺ and Cl^- 

= 564/2 = 282 pm