The potential energy of the orbital electron in the ground state of hydrogen atom is –E. What is the kinetic energy?

Potential energy of their orbital electron in the ground state of a hydrogen atom is given by: $\mathrm{U}=\frac{-{\mathrm{e}}^2}{4\pi {\epsilon }_0\mathrm{r}}=-\mathrm{E}\dots \dots ..\left(1\right)$

Kinetic energy of the orbital electron in the ground state of an hydrogen atom is given by: $K=\frac{e^2}{8\pi {\epsilon }_{0}r}=\frac{1}{2}\left(\frac{{\mathrm{e}}^2}{4\pi {\epsilon }_{0}r}\right)=\frac{\mathrm{E}}{2}$