Chapter 31 - Atomic Physics - Problems and Conceptual Exercises - Page 1111: 3

$5.6pJ$

We can find the required work done as follows: $W_{\infty}=\Delta U=\frac{Kqq_{\circ}}{r}-0$ $\implies W_{\infty}=\frac{(K)(2e)(29e)}{r}$ $W_{infty}=\frac{58Ke^2}{r}$ We plug in the known values to obtain: $W_{\infty}=\frac{(58)(8.99\times 10^{9})(1.60\times 10^{-19})^2}{\frac{1}{2}(4.8\times 10^{-15})}$ $W_{infty}=5.6pJ$