Question

What do you understand by the term electron gain enthalpy? Explain why do electron gain enthalpies of the atoms become more negative, from left to right along a period in the periodic table.

Answer 1

$EGE$ is the energy change associated with gain/add $n$ of an $e^{-}$ in the outermost shell of an atom/molecule.

From left to right along a period in the periodic table the $EGE$ value becomes more negative as on moving across the period electronegativity increases thereby they tend attract $e^{-}$, moreover have the tendency to add $e^{-}$ in their outermost shell to achieve the stable state.