question_answer

If the distance between \[N{{a}^{+}}\] and \[C{{l}^{-}}\] ions in sodium chloride crystal is X pm, the length of the edge of the unit cell is:

A)  \[4X\,pm\]       

B)  \[X/4\text{ }pm\]

C)  \[X/2\text{ }pm\]

D)  \[2X\text{ }pm\]