AP EAPCET 08-Jul-2022 Shift 2 Paper

For hexagonal close packed ( hcp ) crystal, there are 6 atoms per unit cell. That means anion A= number of octahedral voids = number of atoms per unit cell =6.
We also know that, tetrahedral voids
=2×Octahedral‌voids
∴C=

2

3

×(2×6)=8
Hence, C:A=8:6=4:3
Therefore, the formula of the crystal is C4A3.