In a F.C.C. arrangement of A and B atoms whose A atoms are at the corner of the unit cell and B atoms at the face centres. One of the A atom is missing from one corner in unit cell. The simplest formula of compound is
A2B24
Effective number of ‘A’ atoms
=7×18=78
Effective number of ‘B’ atoms
=6×12=3
∴ formula =A78B3=A7B24