Question

The crystalline solids have definite orderly arrangement of their constituent particles in three dimensions known as lattice. The smallest repeating part in the lattice is known as unit cell. The unit cell are described as simple cubic face centred and body centred unit cell.
For the stable ionic crystalline structures, there is definite radius ratio limit for a cation to fit perfectly in the lattice of anions called radius ratio rule. This also defines the coordination number of an ion.
(i) The number of atoms per unit cell in simple cubic $\left(s\right)$, body centred $\left(b\right)$ and face centred $\left(f\right)$ unit cell decreases as:

• A. $f>b>s$
• B. $s>b>f$
• C. $b>f>s$
• D. $f>b=s$

Answer 1

The correct option is A $f>b>s$

The number of atoms per unit cell in simple cubic $(s=1)$, body centred $(b=2)$ and face centred $(f=4)$.
Thus decreasing order of number of atoms is:
$f>b>s$