Answer
$13.6eV$
Work Step by Step
We know that
$W=\frac{1}{2}(\frac{1}{4\pi \epsilon_{\circ}}\frac{e^2}{R})$
We plug in the known values to obtain:
$W=\frac{9\times 10^9Nm^2/C^2(1.602\times 10^{-19}C)^2}{2(0.529\times 10^{-10}m)}$
This simplifies to:
$W=2.18\times 10^{-18}J=13.6eV$
