Answer
$n = 8.49 \times 10^{28} m^{-3}$
Work Step by Step
Use the formula $n = \frac{d}{M}$
where
d = Mass density
M = Mass of single copper atom
n = Number of conduction electrons per unit volume
molar mass of copper A = 63.54 g/mol
Find the M first
$ M = \frac{A}{N_A}$
where $N_A$ is $6.022 \times 10^{23}/mol$
$ M = \frac{63.54 g/mol}{6.022 \times 10^{23}/mol}$
$M = 1.055\times 10^{-22} g$
So
$n = \frac{d}{M}$
$n = \frac{8.96g/cm^3}{1.055\times 10^{-22} g}$
$n = 8.49 \times 10^{28} m^{-3}$
