Question

Pick out the incorrect statement about $CsCl$ structure.

• A. $CsCl$ has a bcc structure
• B. $C{l}^{-}$ ions are present at cubic centres
• C. Coordination no. of both $C{s}^{+}$ and $C{l}^{-}$ is 8
• D. $C{l}^{-}$ adopts a simple cubic lattice

Answer 1

The correct option is B $C{l}^{-}$ ions are present at cubic centres

$CsCl$ crystallizes in a body centred cubic structure where $C{l}^{-}$ ions forms a simple cubic structure with $C{s}^{+}$ ion occupying the body centre.
This type of structure is formed when the anion and cation have similar sizes.

$C{s}^{+}$ ion at the centre is surrounded by 8 $C{l}^{-}$ ions in the corners of the cube. Thus, the coordination number of $C{s}^{+}$ ion is 8.
Each $C{l}^{-}$ ion at the corner is shared by 8 $C{s}^{+}$ from eight unit cells. Thus, the coordination number of $C{l}^{-}$ is 8