Question

How many effective $N{a}^{+}$ ions are present in rock salt $NaCl$ if ions along one axis joining opposite faces are removed?

Answer 1

If ions along one axis joining opposite faces are removed, then $N{a}^{+}$ ion present at octahedral void at body center will be removed.

So, $Z_{newN{a}^{+}}=12\times \frac{1}{4}=3$ (instead of four)