Binding energy of a hydrogen atom is $13.6 \ eV$. The binding energy of a singly ionized helium atom is : ............ $eV$

What will be the energy of an electron emitted from the ground state to the $n^{th}$ orbit?

In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $3^{rd}$ orbit,what is the total number of spectral lines produced?

If the electron of a hydrogen atom is present in the first orbit, the total energy of the electron is

Bohr's radius can have

In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $2^{nd}$ orbit through multiple steps,the number of spectral lines produced is ....