Question

\[MgO\] has \[NaCl\] type structure and \[TiCl\] has \[CsCl\] type? (\[MgO\] and \[TiCl\])

Answer 1

Hint: If we analyze the lattice structure of Sodium Chloride (\[NaCl\]) and, the formula unit of \[NaCl\] (Sodium Chloride) displays a \[1:1\] ratio. Also, the formula unit of cesium chloride displays \[1:1\] ratio.

Complete step by step answer:
Given:
\[MgO\] has \[NaCl\] type structure and \[TiCl\] has \[CsCl\] type structure of ions.
Let us first understand the concept of coordination number.
The coordination number is the number of ions that immediately surround an ion of the opposite charge within a crystal lattice.
Let us now draw the similarity of \[MgO\] and \[NaCl\] structure.
In sodium chloride\[(NaCl)\]structure, the chloride ions are arranged in a face centered arrangement that is chloride ions are present at the corners and face centers of the unit cell. Therefore,

$Total\,number\,of\,chloride\,\,ions\,in\,a\,unit\,cell\,=\,\\dfrac{1}{8}\times 8+\\dfrac{1}{2}\times 6$
$=4$ [$\\dfrac{1}{8}$ is the combination for the corners while $\\dfrac{1}{2}$ is combination
for face centers.]

Thus, we take 4 chlorides ions and 4 $N{{a}^{+}}$ ions (present at the body center and the edge center) to balance each other. Hence, we can easily analyze that $N{{a}^{+}}$ and $C{{l}^{-}}$ are coordinated to 6 other atoms. The coordination number for $M{{g}^{2+}}$ and ${{O}^{2-}}$in \[MgO\] is also 6 for each ion. Thus, \[MgO\] has \[NaCl\] type structure.

Similarly, in cesium chloride crystal, the cesium ion occupies center

 while the chloride ion occupies each corner of the cube. Thus, the
 coordination of both is 8. In TiCl as well \[T{{i}^{+}}\]and \[C{{l}^{-}}\]contain coordination
 number ‘8’. So CsCl and TiCl have the same structure of ions.

Note:
Students must find it very interesting that often the color of a compound is affected by the specific materials coordinated to that central ion.