Question

An ionic compound (a+b) crystallizes in rock salt structure. If the ionic radius of a+andb is 200 pm and 400 pm respectively then distance between nearest cations is x. Find the value of x.

Answer 1

Dear Student,

◆ Answer -

d = 448.6 pm

● Explanation -

Given that compound AB forms crystal structure like rock salt. i.e. FCC with A at corners & B at centre.

Edge length of unit cell of FCC crystal will be -

a = √2 (rA + rB)

a = √2 (200 + 400)

a = √2 × 600

a = 848.6 pm

Minimum distance between two cations is calculated by -

d = a - 2×rA

d = 848.6 - 2×200

d = 448.6 pm

Therefore, Minimum distance between two cations will be 448.6 pm.

Thanks for asking..