State three rules suggested by Bohr and Bury for the distribution of electrons into different orbits (shells) of an atom.

(N/A) $(i)$ The maximum number of electrons present in a shell is given by the formula $2n^2$,where $n$ is the orbit number or energy level index $(1, 2, 3, ...)$.
$(ii)$ The outermost shell of an atom can accommodate a maximum of $8$ electrons.
$(iii)$ Electrons are not accommodated in a given shell unless the inner shells are completely filled; that is,the shells are filled in a stepwise manner.