Exam

NTA Abhyas

Year

2020

Subject

Chemistry

Chapter

Solid State

NTA Abhyas 2020 · Chemistry · Solid State

How many units of NaCl is present per unit cell of NaCl?

How many units of NaCl is present per unit cell of NaCl?

Step-by-step solution

$Cl^{-}$ ions form ccp lattice i.e 8 at corners + 6 at face centres.

$⇒ 8 \times \dfrac{8}{18} + 6 \times \dfrac{1}{2} = 4Cl^{-}ions$

$Na^{+}$ at octahedral voids 12 at centre edges plus one at body centre.

$⇒ 12 \times \dfrac{1}{4} + 1 = 4Na^{+}ions$

i.e $\text{4NaCl}$ molecules per unit cell.