Arrange the elements with the following electronic configuration of valence electron in the decreasing order of ${\mathrm{\Delta }}_{\mathrm{eg}}{\mathrm{H}}^{\mathrm{\Theta }}$.

(A) $3{\mathrm{s}}^{2}3{\mathrm{p}}^4$ (B) $2{\mathrm{s}}^{2}2{\mathrm{p}}^4$ (C) $2{\mathrm{s}}^{2}2{\mathrm{p}}^3$ (D) $2{\mathrm{s}}^{2}2{\mathrm{p}}^5$

Select the equations having endothermic step:

The amount of energy released when a neutral isolated gaseous atom accepts an electron to form gaseous anion is called electron
affinity.

${\mathrm{O}}_{\left(\mathrm{g}\right)}+e^{\ominus }\stackrel{\mathrm{Exothermic}}{⟶}{\mathrm{O}}_{\left(\mathrm{g}\right)}^{\ominus }$  .... (i)

${\mathrm{O}}_{\left(\mathrm{g}\right)}^{\ominus }+e^{\ominus }\stackrel{ \mathrm{Endothermic}}{⟶}{\mathrm{O}}_{\left(\mathrm{g}\right)}^{2-}$ .... (ii)

In (2) the energy has to be supplied for addition of second electron due to repulsion between an anion and extra electron. The members of third period have higher electron affinity value than members of second period.

Which process involves the maximum release of energy?

Calculate the electronegativity of carbon at Pauling's scale?

Given:

${\mathrm{E}}_{\mathrm{H}-\mathrm{H}}=104.2 \mathrm{kcal} {\mathrm{mol}}^{-1}$

${\mathrm{E}}_{\mathrm{C}-\mathrm{C}}=83.1 \mathrm{kcal} {\mathrm{mol}}^{-1}$

${\mathrm{E}}_{\mathrm{C}-\mathrm{H}}=98.8 \mathrm{kcal} {\mathrm{mol}}^{-1}$

Electronegativity of hydrogen $=2.1$