${\mathrm{Cl}}^{-}$ has completely filled K and L shells. Explain. 

The schematic atomic structure of four elements is given below. Observe and choose the right statement.

Match the following :
List -I :
(a) Frequency of distribution of the emitted radiation from a black body
(b) Spin quantum numbers(m_s)
(c) Angular Momentum
(d) All orbital have equal energy

List - II :
(i) degeneracy
(ii) temperature dependent
(iii) vector quantity
(iv) mass times velocity times radius 

Codes:

An isoelectronic species are

$$\begin{gathered} \mathrm{a}\left){\mathrm{Na}}^{+} \\ \mathrm{b}\right){\mathrm{Al}}^{3+} \\ \mathrm{c}\left){\mathrm{Mg}}^{2+} \\ \mathrm{d}\right){\mathrm{Ca}}^{2+} \end{gathered}$$

Two atoms are said to be isobars if 

Nitrogen (atomic number $7$) and phosphorus (atomic number $15$) belong to group $15$  of the Periodic Table. Write the electronic configuration of these two elements. Which one of these will be more electronegative? Why?