Question

Which of the following is TRUE for NaCl type structure?

• A. Cations are present at tetrahedral voids
• B. It has 8:4 coordination.
• C. Cations are present at octahedral voids
• D. It has 6:6 coordination

Answer 1

Answer: (C), (D)

The correct options are
C

Cations are present at octahedral voids

D

It has 6:6 coordination

Just recall the structure of NaCl here.

NaCl $\to$ It has a face-centered cubic (fcc) arrangement (also called cubic close packing, i.e., ccp) in which $C{l}^{⊝}$ ions occupy the corners and face centers of the cube while $N{a}^{\oplus }$ ions are present at the body center and edge centers.

NaCl structure

Each $N{a}^{\oplus }$ ion is surrounded by six $C{l}^{⊝}$ ions and each $C{l}^{⊝}$ ion is surrounded by six $N{a}^{\oplus }$ ions. In other words, the $N{a}^{\oplus }$ ions as well as $C{l}^{⊝}$ ions have coordination number of 6, i.e., this structure has 6 : 6 coordination, i.e., $C{l}^{⊝}$ ions being larger in size are present in the cubic close packing while $N{a}^{\oplus }$ ions are present in all the octahedral voids.