NaCl crystallizes in face-centered cubic cell. what is the total number of ions(Na+ ions and Cr- ions) that lie withing a unit cell of NaCl?

Question

2
4
8
6
5

Answer 1

If I interpret the question correctly, there are 4 Na^+ in a unit cell of NaCl and 4 Cl^- in a unit cell of NaCl making, I suppose, 8 for the total number.

Answer 2

since NaCl crystallizes in face-centered cubic cell, this means that we can have 6 halves of Na+ ions at the phases which makes 3 Na+ ions and 8 of (1\8) ions of Cl-, which make 1 ion of Cl-. Now the total number of ions(Na+ ions and Cl- ions) that lie withing a unit cell of NaCl is given by sum of the ions of Na+ ions and Cl-
(3 Na+ and 1 Cl-= 4 ions )