The radius of the first excited state of a Helium ion $(He^+)$ is given by (where $a_0$ is the radius of the first stationary state of the hydrogen atom):

Bohr’s atomic theory gave the idea of :

The ionization enthalpy of a hydrogen atom is $1.312 \times 10^6 \, J \, mol^{-1}$. The energy required to excite an electron from $n = 1$ to $n = 2$ in the atom is .......

What is the separation energy (in $eV$) for $Be^{3+}$ in the first excited state?

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.

Which among the following electron transitions $(n_2 \rightarrow n_1)$ in a $H$-atom results in the minimum change in its orbit radius $(r_2 - r_1)$?