Q.
Unit cell of $( BN )_{ n }$, i.e. boron nitride, is similar to that of graphite except that each layer consists of alternating $B$ and $B$ -atoms in hexagonal rings. It crystallises in a hexagonal unit cell with $a =0.251\, nm , z =2$ for $( BN )_{ n }$
For graphite, $a =0.2455\, nm$ and distance between $C$ -atoms $=0.1415\, nm$. Thus, distance between $B$ and $N$-atoms is
The Solid State
Solution: