Answer
$n = 1.31 \times 10^{29} m^{-3}$
Work Step by Step
Use the formula $n = \frac{d}{M}$
where
d = Mass density
M = Mass of single zinc atom
n = Number of conduction electrons per unit volume
molar mass of zinc A = 65.37 g/mol and Zinc is bivalent atom.
So
$n = \frac{d}{M}$
$n = \frac{(2)(7.133g/cm^3)}{(65.37 g/mol)(6.022 \times 10^{23}/mol)}$
$n = 1.31 \times 10^{29} m^{-3}$
