Answer
$n = 5.86 \times 10^{28} m^{-3}$
Work Step by Step
For silver,
$M = 107.870 g/mol$
$\rho = 10.49 kg/m^3$
Avogadro number $N_A = 6.022 \times 10^{23}/mol$
The formula for number density
$n = \frac{\rho}{M_0}$
Where
$M_0 = \frac{M}{N_A}$
$M_0 = \frac{107.870 g/mol}{6.022 \times 10^{23}/mol}$
$M_0 = 1.791 \times 10^{-25} kg$
Solve for n
$n = \frac{10.49 kg/m^3}{1.791 \times 10^{-25} kg}$
$n = 5.86 \times 10^{28} m^{-3}$
