A unit cell consists of a cube in which there are A atoms at the corners and B atoms at the face centres. Two A atoms are missing from the two corners of the unit cell. What is the formula of the compound ?

Answer

`AB_4`

Explanation

No. of A atoms at the corners = 8
No. of A atoms missing from corners = 2
No. of A atoms present = 8 - 2 = 6
No. of A atoms per unit cell = `6/8 = 3//4`
No. of B atoms per unit cell = `6 xx 1/2 = 3`
`:. " Formula" = A_(3//4)B_(3) = AB_(4)`.