Question

Starting from the rock salt structure, the crystal structure type generated by the removal of all ions of one types is:
A. Simple cubic
B. Body-centered cubic
C. Face-centered cubic
D. End-centered cubic

Answer 1

Hint: For solving this question, let’s first start from the structure of the rock salt. In rock salt, the sodium ions occupy octahedral holes and chloride ions have face-centered cubic arrangement. When all the sodium ions are removed from the structure then we are left with face-centered cubic arrangement of the chloride ions.

Complete answer:
First we need to understand what rock salt is?
Rock salt i.e. $NaCl$ is an ionic compound that naturally occurs as white crystals. The salt is extracted from the mineral form of halite. The structure is formed by repetition of the face centered cubic unit cell. The stoichiometry ratio of $NaCl$ is 1:1 and has a molar mass of 58.4 g/mol. Here, the compounds of sodium chloride include alkali halides, metal oxides and transition-metal compounds.
We need to remember that the rock salt structure has applications like structure and dynamics of water, crystallization of proteins and conformational behavior of peptides and nucleic acids.
With the help of this figure we can understand the structure of rock salt better.

Here, in this figure, the small purple spheres are representing sodium cations, $N{a^ + }$ and the bigger green spheres represent chloride anions, $C{l^ - }$ .
And hence Rock salt has FCC structure so the option C is the correct answer.

Note:
In a unit cell, there are four different sites i.e. center site, face site, edge site and corner site. With the help of these sites we can determine the number of ions $N{a^ + }$ and $C{l^ - }$ ions in the unit cell of$NaCl$. On counting the total number of ions, we get to know that the corner site is shared by 7 other unit cells. As $NaCl$ is a face centered cubic unit cell so it has four cations and anions respectively.