Question

The depictions of ionic compounds do not show distinct compound units but rather a collection of ions in the ratio given by the formula. Explain how the drawing of NaCl both illustrates that the compound exists as a large collection of ions and that the ratio of sodium ions to chloride ions is 1-to-1 as indicated by the formula NaCl.

Answer 1

The ionic compound NaCl has a Face Centered Cubic unit cell

The site for atoms are Face, center and Edges corner.

Effective number of atoms

Na+

1centers + 12edges x
`(1)/(4)` = 4 Na+

Cl-

6face x
`(1)/(2)` +
`(1)/(8)` x8 corners = 4Cl-

This is just one unit cell effective atom, there are thousand's of such unit cells are combined to form one such structure of NaCl. The real formula of NaCl is Na4Cl4 but for simplicity we use empirical formula that is NaCl.