\textbf{197.} In the hydrogen atom, the electric potential energy of the electron in the electric field of the nucleus is equal to which of the following? ($r$ is the radius of the electron's orbit and $k$ is Coulomb's constant.)
\[
\text{(1)}\ \frac{ke^2}{2r} \qquad \text{(2)}\ -\frac{ke^2}{2r} \qquad \text{(3)}\ \frac{ke^2}{r} \qquad \text{(4)}\ -\frac{ke^2}{r}
\]