Question

A cube of any crystal A-atom placed at every corners and B-atom placed at every centre of face. The formula of compound:

• A. $AB$
• B. $AB_3$
• C. $A_2B_2$
• D. $A_2B_3$

Answer 1

Answer: (B)

$AB_3$

Answer 2

$A$ atoms are at 8 corners of the cube.
Thus, no. of $A$ atoms per unit cell = $8 \times \frac 18$ = 1

$B$ atoms are at the face centre of six faces.
Thus, no. of $B$ atoms per unit cell = $6 \times \frac 12$ = 3

the formula of the compound is AB3

So, the correct option is (B): $AB_3$