The electronic structure of four elements a,b,c and d are

$$\begin{gathered} \text{ a) }1{\mathrm{s}}^2 \\ \text{ b) }1{\mathrm{s}}^2,2{\mathrm{s}}^2,2{\mathrm{p}}^2 \\ \text{ c) }1{\mathrm{s}}^2,2{\mathrm{s}}^2,2{\mathrm{p}}^5 \\ \text{ d) }1{\mathrm{s}}^2,2{\mathrm{s}}^2,2{\mathrm{p}}^6 \end{gathered}$$

The tendency to form an electrovalent bond is greatest in

a)1s² (douplet)Stable electronic configuration 

b)1s²2s²2p² $\Rightarrow$2 electrons are required to get octet configuration

c)1s²2s²2p⁵ $\Rightarrow$1 electron is required to get octet configuration

The element with an electronic structure requires only one electron to complete its octet and it will form an anion so it will form an electrovalent bond 

d)1s²2s²2p⁶ $\Rightarrow$stable (octet ) electronic configuration