The energy of electron in hydrogen atom when present in $n=1, n=2$ and $n=3$ will be in the ratio of

The radius of first Bohr orbit of hydrogen atom is same as that of orbit $(n)$ of hydrogen like species $X .(n)$ and $X$ respectively are

Identify the impossible quantum number set for the electron from the following.

The hybridisations of the central atom in the molecules $\mathrm{BF}_3, \mathrm{BeF}_2, \mathrm{BrF}_3$ are respectively.