Question

The anions A from hexagonal close packing and atoms (M) occupy only two-third of the octahedral voids. The general formula of the compound is
A. `M_2A_3`
B. MA
C. `MA_2`
D. `M_3A_2`

Answer 1

Correct Answer - A
In hexagonal close packing, one sphere is in contact with 12 spheres .
Thus , the number of anion A per unit cel = 12
Octahedral voids = number of spheres = 12
`therefore` number of M atoms per unit cell
`=2/3 " of octahedral voids " = 2//3 xx12 =8`
`rArr` A:M = 12:8=3:2
`therefore " The formula of the compound is " M_2A_3` .