Question

In $ Na_{2}O $ , having ant fluorite structure

• A. oxide ions have a cubic close packed arrangement and $ Na^{+} $ occupy all the eight tetrahedral voids
• B. oxide ions have a cubic close packed arrangement and $ Na^{+}$ occupy all the octahedral voids
• C. $ Na^{+} $ ions have a cubic close packed arrangement and $ O^{2-} $ occupy all the octahedral voids
• D. $ N^{+} $ ions have a cubic close arrangement and $ O^{2-} $ occupy all the tetrahedral voids

Answer 1

Answer: (A)

In antifluorite structure, $O ^{2-}$ ions occupy half of the cubic holes and $Na ^{+}$occupy all tetrahedral voids, eg, $Na _{2} O .$
$ O ^{2-}$ are surrounded by $8 Na ^{+}$ions and $Na ^{+}$are surrounded by $40^{2-}$ ions.
So, it has $4: 8$ coordination.