Question

Would you expect the second electron gain enthalpy of O as positive, more than negative or less negative than the first? Justify your answer.
What is the basic difference between the terms electron gain enthalpy and electronegativity?

Answer 1

$O\left(g\right)+e\to O^{-}\left(g\right)$ $:$ $\Delta H=-141K/mol$

$O^{-}\left(g\right)+e\to O^{2-}\left(g\right)$ $:$ $\Delta H=+780KJ/mol$

First electron gain enthalpy of Oxygen is negative but when another electron is added to $O^{-}$ ion to form ${O^2}^{-}$ ion it feels stronger electrostatic repulsion$.$ Hence$,$ when we add $2^{nd}$ electron then energy absorb by it$.$ That's why the $2^{nd}$ electron gain enthalpy of oxygen is positive.

Electronegativity$:$ It is the ability of an atom to attract the shared or bonded of electrons$.$

Electron gain enthalpy$:$ It is the energy charge that occurs when an electron is added to the outermost shell of a neutral gaseous atom$.$