#### Answer

$\frac{N_{v}}{N} = 6.08 \times 10^{-16}$

#### Work Step by Step

Given:
Copper with melting temperature of 1084°C (1357K)
energy of vacancy formation is 0.90 eV/atom
Required:
fraction of atom sites that are vacant at room temperature (298K).
Solution:
Using Equation 4.1:
$\frac{N_{v}}{N} = exp (-\frac{Q_{v}}{kT}) = exp (-\frac{0.90 eV/atom}{(8.62 \times 10^{-5} eV/atom-K)(298 K)} = 6.08 \times 10^{-16}$