Question

In a hexagonal-close-pack (hcp) unit cell, the ratio of lattice points to octahedral holes to tetrahedral holes is 1:1:2.

What is the general formula for a compound if anions occupy the hcp lattice points and cations occupy all the octahedral holes?What is the general formula for a compound if anions occupy the hcp lattice points and cations occupy all the octahedral and tetrahedral holes?

Answer 1

Step-by-step explanation:

In a hexagonal-close-pack (HCP) unit cell, the ratio of lattice points to octahedral holes to tetrahedral holes = 1 : 1 : 2

let the :

Number of lattice point = 1x.

Number of octahedral points = 1x

Number of tetrahedral points = 2x

If anions occupy the HCP lattice points and cations occupy half of the octahedral holes.

Number of anions occupying the HCP lattice points, A= 1x

Number of cations occupying the octahedral points, B = 1x

The formula of the compound will be =
`A_(1x)B_(1x)=AB`

If anions occupy the HCP lattice points and cations occupy all of the octahedral and the tetrahedral holes.

Number of anions occupying the HCP lattice points, A= 1x

Number of cations occupying the octahedral points, B = x

Number of cations occupying the tetrahedral points, B = 2x

total number of cations = x + 2x = 3x

The formula of the compound will be =
`A_(1x)B_(3x)=AB_3`