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

Explanation

(i) It is given that the atoms of A are present at the corners of the cube.
(ii) Therefore, number of atoms of Q in one unit cell `= 8 xx ( 1)/(8) = 1 `
( iii) It is also given that the atoms of P are present at the body - centre.
(iv) Therefore, number of atoms of P in one unit cell.
(v) This means that the ratio of the number of P atoms to the number of Q atoms,
`P : Q =1 :1`,
(vi) Hence, the formula of the compound is PQ.
(vii) The coordination number of both P and Q is 8.