If the electron of a hydrogen atom is in the third orbit,it represents its ...... excited state.

The kinetic energy of an electron in the second Bohr orbit of a hydrogen atom is [$a_0$ is Bohr radius]:

The energy of an electron in the first orbit of a hydrogen atom is $-13.6 \ eV$. The possible energy value for an electron in the excited state is ............ $eV$.

Calculate the radius of the first orbit of $Li^{2+}$. (in $pm$)

The angular momentum of an electron in a stationary state of $Li^{2+} (Z=3)$ is $\frac{3h}{\pi}$. The radius and energy of that stationary state are respectively:

The energy required to release $1$ electron from $He^{+}$ is $............$ $eV$.