Question

Calculate the third Bohr's energy of the hydrogen atom

Answer 1

The orbital energy for nth level is

$$E_n=-\frac{2\pi e_e^4m_ek^2}{h^2n^2}=-\frac{13.6\text{ eV}}{n^2},\\ \space\\ E_3=-\frac{13.6}{3^2}=-1.51\text{ eV}.$$