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The Solid State

Question
CBSEENCH12011171

A structure of a mixed oxide is cubic close packed (ccp). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are occupied by a monovalent metal B. The formula of the oxide is

  • ABO2

  • A2BO2

  • A2B3O4

  • AB2O2

Solution

D.

AB2O2

According to ccp,
Number of O2- ions = 4
So, tetrahedral void = 8
and octahedral void = 4
Since A ions occupied 1/4th of the tetrahedral void.
Therefore,
Number of A ions = 1/4 x 8 = 2
Again, B ions occupied all octahedral void.
Therefore, Number of B ions = 4 
A: B:O = 2:4:4
 = 1:2:2
Structure of oxide= AB2O2