The energy required to dislodge an electron from an excited isolated $H^-$ ion,given that the ionization energy of a ground state $H$ atom is $IE_1 = 13.6 \ eV$,is:

State whether the following statements are true or false:
$(i)$ The $Bohr$ model cannot explain how atoms form molecules.
$(ii)$ The $Bohr$ model is accepted as the planetary model.
$(iii)$ Electrons in an atom do not absorb or emit energy while moving in a stationary orbit.
$(iv)$ The spectral lines of the $Brackett$ series are found in the ultraviolet region.

The radius of the first Bohr orbit for hydrogen is $0.53 \ \mathring{A}$. The radius of the third Bohr orbit would be .............. $\mathring{A}$.

The work functions (in $eV$) of $Mg, Cu, Ag, Na$ respectively are $3.7, 4.8, 4.3, 2.3$. From how many metals,the electrons will be ejected if their surfaces are irradiated with an electromagnetic radiation of wavelength $300 \ nm$ ?
$(h=6.6 \times 10^{-34} \ Js, 1 \ eV=1.6 \times 10^{-19} \ J)$

For which of the following,the radius will be the same as that of a hydrogen atom having $n = 1$?

Wave number of a spectral line for a given transition is $y \ cm^{-1}$ for $He^{+}$,then its value for $Li^{2+}$ for the same transition is