Question

If three elements P, Q and R crystallise in a cubic unit cell with P atoms at the corners, Q atoms at the cubic centre and R atoms at the centre of each face of the cube, then write the formula of the compound.

Answer 1

Contribution made by the atoms of P present in all eight conrners of the cube
`=1//8xx8=1`
Contribution made by the atoms of Q present in the centre of body = 1
Contribution made by the atoms of R present at all the six faces `=1//2xx6=3`
`therefore` Formula of the compound = `PQR_(3)`