Angular momentum of an electron in the $M$-shell of a $Li^{+2}$ ion is:

The ionization energy of a hydrogen atom is $13.6 \, eV$. What is the energy required (in $eV$) to excite the electron from the ground state to the first excited state?

What is the wave number of the lowest energy transition in the Balmer series?

The radius of the second Bohr orbit for hydrogen atom is .......... $\mathring{A}$.
(Planck's constant $h = 6.626 \times 10^{-34} \, Js$; mass of electron $= 9.1091 \times 10^{-31} \, kg$; charge of electron $e = 1.60210 \times 10^{-19} \, C$; permittivity of vacuum $\epsilon_0 = 8.854185 \times 10^{-12} \, C^2 N^{-1} m^{-2}$)

If change in energy $(\Delta E) = 3 \times 10^{-8} \ J$,$h = 6.64 \times 10^{-34} \ J \cdot s$ and $c = 3 \times 10^8 \ m/s$,then the wavelength of the light is:

The spectrum of $Li^{2+}$ is similar to that of: