Question

Potassium fluoride has NaCl type structure. What is the
distance between K⁺ and F⁻ ions if cell edge is ‘a’ cm.
(a) 2a cm (b) a/2 cm
(c) 4a cm (d) a/4 cm

Answer 1

The  distance between K⁺ and F⁻ ions is a/2 cm if cell edge is ‘a’ cm. That's why option b is correct.

Explanation:

The sodium chloride unit cell has face centered cubic (fcc) structure. Potassium fluoride also has fcc structure.

The distance between K⁺ and F⁻ is 1/2 × edge length.

If edge length is "a cm" then distance is a/2 cm