The ionization energy of a singly ionized helium ion $(He^+)$ is equal to:

The Bohr radius of a hydrogen-like species is $70.53 \text{ pm}$. The species and the stationary state $(n)$ are respectively (Given: Hydrogen atom Bohr radius is $52.9 \text{ pm}$)

State whether the following statements are true or false:
$(i)$ When an electron in a hydrogen atom returns from the third excited state to the ground state,it emits frequencies corresponding to lines in the Lyman,Balmer,and Paschen series.
$(ii)$ When an electron in a hydrogen atom returns from the third excited state to the ground state,it emits radiation with wavelengths corresponding to the Pfund series,which has very high frequencies.

If the radius of the first orbit of a hydrogen-like ion is $1.763 \times 10^{-2} \ nm$, the energy associated with that orbit (in $J$) is

In the ground state of $He^{+}$ ion,how much energy must be supplied to the electron so that the second line of the Balmer series is obtained in its spectrum? ................. $eV$

The radius of the $2^{nd}$ orbit of $B^{4+}$ ion is: