Trends in Physical Properties - Electron Gain Enthalpy

Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is ______.

Which of the following pair of elements would have a more negative electron gain enthalpy?

F or Cl

The formation of the oxide ion, \[\ce{O2- (g)}\], from oxygen atom requires first an exothermic and then an endothermic step as shown below:

\[\ce{O (g) + e- -> O- (g) ; ∆H^Θ = - 14 kJ mol^{-1}}\]

\[\ce{O- (g) + e- -> O^{2-} (g) ; ∆H^Θ = + 780 kJ mol^{-1}}\]

Thus process of formation of \[\ce{O^{2-}}\] in gas phase is unfavourable even though \[\ce{O^{2-}}\] is isoelectronic with neon. It is due to the fact that,

In which of the following options the order of arrangement does not agree with the variation of the property indicated against it?

(i) \[\ce{Al^{3+} < Mg^{2+} < Na+ < F-}\] (increasing ionic size)

(ii) \[\ce{B < C < N < O}\] (increasing first ionisation enthalpy)

(iii) \[\ce{I < Br < Cl < F}\] (increasing electron gain enthalpy)

(iv) \[\ce{Li < Na < K < Rb}\] (increasing metallic radius)

Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.

Describe the theory associated with the radius of an atom as it gains an electron.

Describe the theory associated with the radius of an atom as it loses an electron.

Which of the following pair of elements would have a more negative electron gain enthalpy?

O or F