The maximum energy is present in any electron at

If the velocity of an electron in the $n^{th}$ orbit of a hydrogen atom is $0.0109 \times 10^{10} \, cm \, s^{-1}$,what is the value of $n$?

The wavelength of the first line of the Balmer series is $656 \ nm$. Calculate the wavelength of the second line of this series. (Note: First line means $n=3 \to n=2$ and second line means $n=4 \to n=2$)

The ionization energy of $He^+$ is $19.6 \times 10^{-18} \ J \ atom^{-1}$. What is the energy of the first stationary state $(n = 1)$ of $Li^{2+}$?

If the shortest wavelength of $H$ atom in Lyman series is $x$,then the longest wavelength in Balmer series of $He^{+}$ is

The radius of the electron in the first excited state of a hydrogen atom is: