If the ionization energy of a hydrogen atom is $E$,then the ionization energy of $Li^{2+}$ will be ............ $E$.

For which of the following species,Bohr's theory is not applicable?

The wavelength of the first line of the Lyman series for hydrogen is $1216 \ \mathring{A}$. The wavelength of the first line of the same series for a $10$ times ionized sodium atom $(Z = 11)$ will be ......... $\mathring{A}$.

Which transition in a $H$ atom has the same wavelength as the transition from $n = 4$ to $n = 2$ in a $He^{+}$ ion?

In which transition is minimum energy emitted?

The wavenumber of the first line $(n_2=3)$ in the Balmer series of hydrogen is $\bar{\nu}_1 \ cm^{-1}$. What is the wavenumber (in $cm^{-1}$) of the second line $(n_2=4)$ in the Balmer series of $He^{+}$?