Chemistry

Problem

In which of the following processes energy is absorbed? a.

\text{Cl} + e^- \longrightarrow \text{Cl}^-

\text{O}^- + e^- \longrightarrow \text{O}^{2-}

\text{O}^{2-} - e^- \longrightarrow \text{O}^-

\text{Na}^+ + e^- \longrightarrow \text{Na}