Match the following columns.

	Column I (Distribution of particles ,A and B)		Column II (Formula)
A	A - At the corners and face centres B - At the edge centres and body centre	1	AB3
B	A - At the corners B - One on each body diagonal	2	AB
C	A - At the corners B - At face centres	3	AB4

(A). A atoms are at the corners and face centers, so number of A atoms $=8\times \frac{1}{8}+\frac{1}{2}\times 6=1+3=4$
                                                                                                       corner atoms       Face center atoms
    B atoms are at the edge centers and body center, so number of B atoms per unit cell $=12\times \frac{1}{4}+1=3+1=4$
     Ratio of A and B = 4 : 4 = 1:1 so formula is AB.
(B).A atoms are at the corners, so number of A atoms per unit cell $=8\times \frac{1}{8}=1\text{ atom. }$
   B atoms are at the body diagonals, so number of B atoms per unit cell = 4 x 1 = 4.
   $\therefore$ Formula of molecule = AB₄.
(C). When A atoms are at the corners and B atoms are at face centers, the formula is AB₃.