The electronic configuration of an element with atomic number $7$ i.e. nitrogen atom is

The atomic number of the element having the maximum number of unpaired electrons (in the ground state) is ........

$(i)$ Write the electronic configurations of the following ions:
$(a)$ $H^{-}$
$(b)$ $Na^{+}$
$(c)$ $O^{2-}$
$(d)$ $F^{-}$
$(ii)$ What are the atomic numbers of elements whose outermost electrons are represented by
$(a)$ $3s^{1}$
$(b)$ $2p^{3}$ and
$(c)$ $3p^{5}$?
$(iii)$ Which atoms are indicated by the following configurations?
$(a)$ $[He] 2s^{1}$
$(b)$ $[Ne] 3s^{2} 3p^{3}$
$(c)$ $[Ar] 4s^{2} 3d^{1}$

The energy of an electron of $2p_y$ orbital is

Number of unpaired electrons in the ground state of beryllium atom is

The allowed set of quantum numbers for an electron in a hydrogen atom is