Solid State Question 181

Question: An ionic compound has a unit cell consisting of A ions at the corners of a cube and B ions on the centres of the faces of the cube. The empirical formula for this compound would be

[CBSE PMT 2004; AIEEE 2005]

Options:

A) $ AB $

B) $ A_2B $

C) $ AB_3 $

D) $ A_3B $

Show Answer

Answer:

Correct Answer: C

Solution:

A atoms are at eight corners of the cube. Therefore, the no. of A atoms in the unit cell = $ \frac{8}{8}=1 $ . B atoms are at the face centre of six faces. Therefore, its share in the unit cell = $ \frac{6}{2}=3 $ . The formula is AB3.