Question

In sodium chloride, $C{l}^{-}$ ions form ccp arrangement. Which site will $N{a}^{+}$ ions occupy in this structure?

• A. Cubic
• B. Tetragonal
• C. Octahedral
• D. Trigonal bipyramidal

Answer 1

The correct option is C Octahedral

In $NaCl,C{l}^{-}$ ions forms fcc structure lattic. Thus, $C{l}^{-}$ present at the corners and face centres of the cube.
Here, $N{a}^{+}$ ions occupies all the octahedral voids. The octahedral voids are present at the edge centres and body centre of the unit cell. The tetrahedral voids of this ccp arrangement is vacant.
Experimentally, the radius ratio of $NaCl$ is comes out to be 0.51
Since,
$0.414<0.51<0.732$
The coordination number of $NaCl$ is 6.
Thus, $N{a}^{+}$ occupies the octahedral voids.