Question

The process(es) requiring the absorption of energy is(are) :

• A. $Cl\to C{l}^{-}$
• B. $O^{-}\to O^{2-}$
• C. $F{e}^{3+}\to F{e}^{2+}$
• D. $Ar\to A{r}^{-}$

Answer 1

Answer: (B), (D)

The correct options are
B $O^{-}\to O^{2-}$
D $Ar\to A{r}^{-}$

A) When a neutral chlorine atom accepts an electron to from chloride anion, energy is released which is equal to the electron affinity of chlorine.
B) When an electron is added to $O^{-}$ anion to form $O^{2-}$ ion, energy is required to overcome the force of repulsion. Thus, the second electron affinity of oxygen is an endoergic process. It is equal to +780 kJ/mol.
C) When Fe(III) ion accepts an electron to form Fe(II) ion, energy is released.
D) When an argon atom accepts an electron to form $A{r}^{-}$ anion, energy is required as the stable configuration $\left(n{s}^{2}n{p}^6\right)$ is broken.