# Why can't we use sodium chloride solution to get the sodium metal?

Because the solution only contains ${\text{Na}}^{+}$ and ${\text{Cl}}^{-}$ ions, and water, and not the metal $\text{Na} \left(s\right)$. You cannot evaporate the water from the solution and hope to obtain anything but $\text{NaCl} \left(s\right)$.
$\text{Na} \left(s\right)$ has an electron configuration of $1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{1}$, but ${\text{Na}}^{+} \left(a q\right)$ has an electron configuration of $1 {s}^{2} 2 {s}^{2} 2 {p}^{6}$. That means they are not the same element, and thus, there is no straightforward way of extracting $\text{Na} \left(s\right)$ from a $\text{NaCl} \left(a q\right)$ solution.
(crudely speaking, you would have to supply an electron for every atom of ${\text{Na}}^{+} \left(a q\right)$ in the solution, which is quite hard to do. You would also have to "undissolve" the particles and collect them into a lattice of metal $\text{Na}$ atoms, which is even harder.)