Question

A compound of X and Y crystallizes in ccp structure in which the X atoms occupy the lattice points at the corners of cube and Y atoms occupy the centres of each of the cube faces. The formula of this compound is ____________.

Options

• XY

• XY₂

• XY₃

• X₂Y₃

Answer 1

A compound of X and Y crystallizes in ccp structure in which the X atoms occupy the lattice points at the corners of cube and Y atoms occupy the centres of each of the cube faces. The formula of this compound is XY₃.

Explanation:

The unit cell of the compound contains one-eighth of each comer atom (X) and one-half of each face centred atom (Y).

Thus, the number of X atoms per unit cell = `8 xx 1/8` = 1

The number of Y atoms per unit cell = `6 xx 1/2` = 3

The formula of the compound is XY₃.