In the atomic spectrum of hydrogen,the series of lines observed in the visible region is:

The nuclear theory of the atom was put forward by:

When an electron transitions from the $6^{th}$ orbit to the $2^{nd}$ orbit in a $H$ atom,what is the total number of spectral lines (excluding the Balmer series) produced?

The energy of an electron in an excited hydrogen atom is $-3.4 \, eV$. According to Bohr's theory,the angular momentum of this electron in $J \cdot s$ is:

In the case of a hydrogen atom,when an electron falls from a higher energy level to the $M$ shell,the corresponding spectral line will form a part of:

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