Question

The unit cell of a NaCl lattice

• A. Is body centred cube
• B. Has ions
• C. Has 4NaCl units
• D. Is electrically charged

Answer 1

Answer: (C)

The explanation for the correct option

Option(A) Has 4 NaCl units.

• NaCl has a cubic unit cell
• In which the sodium ion is occupying all the octahedral sites.
• ... hence the number of sodium ions:

$N{a}^{+}=1+12\times \frac{1}{4}$

$=4sodiumionstotalpercell$

• The chloride ions are ​​at the corners and at the center of each face of the cube. hence the number of chloride ions:

$C{l}^{-}=4\times \frac{1}{2}+8\times \frac{1}{8}$

$=4chlorideionstotalperCell$

• ​Hence, The unit cell of a NaCl lattice has 4 NaCl units.

The explanation for the incorrect option

(B) Is electrically charged- it is not electrically charged in its solid state but it conducts electricity in its molten state.

(C) Has 3 $N{a}^{+}$ ions- it contains 4 $N{a}^{+}$ ions in a unit cell

(D) Is body-centered- It is not body-centered, all the chloride ions have FCC lattice, and the sodium ions are occupying in the octahedral voids.

Hence, Option(A) is correct, The unit cell of a NaCl lattice has 4 NaCl units.