The ratio between kinetic energy and the total energy of the electrons of a hydrogen atom according to Bohr's model is

For hydrogen-like species,which of the following graphs provides the most appropriate representation of $E$ vs $Z$ plot for a constant $n$?
[$E$: Energy of the stationary state,$Z$: atomic number,$n$: principal quantum number]

In the hydrogen atomic spectrum,a series limit is found at $12186.3 \ cm^{-1}$. To which series does it belong?

The nuclear theory of the atom was put forward by:

The energy required for the ionization of an excited hydrogen atom would be (in $eV$)-

If $n=2$ for $He^{+}$ ion,then what is the wavelength in $\mathring{A}$?