A cube solid is made up of two elements P and Q. Atoms Q are present at the corners of the cubic and atom P at the body centre. What is the formula of the compound ? What are the co-ordination numbers of P and Q ?

Explanation

Contribution of 8 atoms of Q present at the eight corners of the cube to the unit cell = 8 = 1
Contribution by 1 atom of P present at the body centre to the unit `8xx1/(8)=1`
`therefore` Formula of the compound : QP
Coordination number of P = 8
(Co-ordination of atom present at cubic site = 8)
`therefore` Coordination number of Q = 8
(Since the compound, involves 1 : 1 co-ordiantion).