Question

An element A and B constitute bcc type crystalline structure. Element A occupies body center position and B is at the corners of a cube. What is the formula of the compound? What are the coordination number of A and B?

Answer 1

$A$ and $B$ constitute to form bcc type crystal structure.

Now, since $A$ is present at body center,

So, effective number of atoms of $A$ in unit cell $=1$

$B$ is present on the corners of the cube, so

Effective number of atoms of $B=\frac{1}{8}\times 8=1$

So, $A:B=1:1$. Hence formula of compound is $AB$

Now, each $A$ atom is surrounded by $8$ $B$ atoms. So, coordination number of both $A$ and $B$ is $8$.