The energy of an electron in the first Bohr orbit of the hydrogen atom is $-13.6 \ eV$. Calculate the energy of an electron in the first Bohr orbit of $He^{+}$ in $eV$.

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

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 ionization potential of hydrogen atom is $13.6 \ eV$. The energy required to remove an electron from the $n = 2$ state of hydrogen atom is : ............ $eV$

The radius of the first Bohr orbit of a hydrogen atom is $0.53 \times 10^{-8} \ cm$. The velocity of the electron in the first Bohr orbit is

The electron in a hydrogen atom undergoes a transition from higher orbits to an orbit of radius $476.1 \text{ pm}$. This transition corresponds to which of the following series?