If three elements P, Q and R crystalline in a cubic solid lattice with P atoms of the corners, Q atoms at the cube centres and R atoms at the centre of the edges, then write the formula of the compound.

Explanation

Contribution of P atoms in unit cell `=1/8`

Number of P atoms in unit cell`=8xx1/8=1`
Contribution of Q atoms in unit cell = 1
Number of R atoms in unit cell = `1/4`
Number of R atoms in unit cell `=1/4xx12=3`
Formula of unit cell = `PQR_3`