Chapter 6, Problem 82E

Of the five elements Al, Cl, I, Na, Rb, which has the most exothermic reaction? (E represents an atom.) What name is given to the energy for the reaction? Hint: note the process depicted does not correspond to electron affinity ${\text{E}}^{+}\left(g\right)+{\text{e}}^{-}\to \text{E}\left(g\right)$