Question

# The process requiring the absorption of energy is:A. $F\to {{F}^{-}}$B. $H\to {{H}^{-}}$C. $Cl\to C{{l}^{-}}$D. $O\to {{O}^{2-}}$

Hint: To add one or more electrons to atoms or atoms to accept electrons require some amount of energy, that is energy is supposed to absorb from others is called absorption energy. Without the involvement of absorption energy maximum atoms won’t accept electrons.

Let us first have a look at option A,
$F\to {{F}^{-}}$
In the above equation, fluorine accepts one electron. We know that the atomic number of fluorine is 9 and in order to get octet configuration fluorine readily accepts one single electron from other atoms. So, fluorine doesn’t need a large amount of energy to absorb single electrons. Therefore option A is wrong.
Now ,coming to option B,
$H\to {{H}^{-}}$
In the above reaction hydrogen accepts one electron. A Hydrogen atom has only one electron in its electronic configuration in ground state. Thus, in order to fill the 1s orbital hydrogen accepts one electron from another donor atom. This reaction also doesn’t need a lot of energy to complete the reaction, so this option is also wrong.
Let us look at option C,
$Cl\to C{{l}^{-}}$
In the above reaction chlorine readily accepts an electron as chlorine has a valence of 7 electrons. To get octet configuration chlorine accepts one electron. Therefore, chlorine also does not absorb much energy.
Finally , coming to option D,
$O\to {{O}^{2-}}$
In the above reaction oxygen accepts two electrons. Oxygen has six valence electrons in its electronic configuration. So, when oxygen accepts one electron then it will get a negative charge. But when the second electron is being added to oxygen then there is a chance to occur repulsion due to the negative charge which is already present on the oxygen ion.
Accordingly, a large amount of energy has to be provided to get${{O}^{2-}}$.
Therefore, we can say that the process requiring the absorption of more energy is$O\to {{O}^{2-}}$.

So, the correct option is D.

Note: If an atom or molecule absorbs energy in a particular reaction then it is an endothermic reaction.
If an atom or molecule releases energy in a particular reaction then it is an exothermic reaction.