The electron in the hydrogen atom undergoes a transition from higher orbitals to an orbital of radius $211.6 \text{ pm}$. This transition is associated with:

Which observations are not explained by the electromagnetic theory of physics?

The statements
$i$. In filling a group of orbitals of equal energy,it is energetically preferable to assign electrons to empty orbitals rather than pair them into a particular orbital.
$ii$. When two electrons are placed in two different orbitals,energy is lower if the spins are parallel.
Are valid for

The angular momentum of an electron in a given orbit is $J$. Its kinetic energy will be:

Find out the distance between the $2^{nd}$ and $3^{rd}$ orbit of the $H^{-}$ ion.

The wave number of the first line of the Balmer series in the hydrogen spectrum is $15200 \, cm^{-1}$. What will be the wave number of the first line of the Balmer series for the $Li^{2+}$ ion in $cm^{-1}$?