Question

What is the co-ordination number of sodium in $Na_2O$ ?

• A. 6
• B. 4
• C. 8
• D. 2

Answer 1

Answer: (B)

4

Answer 2

$Na _{2} O$ has antifluorite structure. $O ^{2-}$ ions constitute a ccp lattice and $Na ^{+}$ ions occupy the tetrahedral voids, each $O ^{2-}$ ion is in contact with $8 Na ^{+}$ ions and each $Na ^{+}$ ion is in contact with $4 O ^{2-}$ ions. Thus $C$. $N$. of sodium in $Na _{2} O =4$.