Normally,the time taken in an electronic transition is approximately:

The wavelength of the radiation emitted,when in a hydrogen atom an electron falls from infinity to stationary state $n = 1$,would be ........ $nm$ (Rydberg constant $R_H = 1.097 \times 10^7 \ m^{-1}$)

First and second excitation potentials of hydrogen atom (in $eV$) would be respectively

If the wave number of radiation emitted for the electron transition from an excited state to ground state of hydrogen is $\frac{5x}{36} \ m^{-1}$,the wave number of radiation absorbed for the electron transition from the above excited state to the next immediate excited state in $m^{-1}$ is:

What is the energy associated with the fourth orbit of a hydrogen atom?
$R_H = 2.18 \times 10^{-18} \ J$

The energy of an electron in the first Bohr orbit of $H$-atom is $-13.6 \ eV$. The possible energy value of an electron in the first excited state of $Li^{2+}$ is (in $eV$)