Question

Sodium crystallizes in the cubic lattice and the edge of the unit cell is $430pm$. Calculate no of atoms in the unit cell.
[atomic mass of sodium = $23.0$ amu.
density of sodium = $0.9623$ g $c{m}^{-3}$.]

• A. 4
• B. 3
• C. 2
• D. 5

Answer 1

Answer: (C)

2

$\rho =0.9623$ $gc{m}^{-3}$

$M_{Na}=23$ $amu$

$a=4.3\mathring{A}$

$Z=?$

$\rho =\frac{Z\times M_A}{N_A\times a^3}$

$⟹0.9623=\frac{Z\times 23}{6.023\times {10}^{23}\times 79.5\times {10}^{-24}}$

$⟹Z=2$