Question

Among halogens, the correct order of amount of energy released in electron gain enthalpy is:
A.$F > Cl > Br > I$
B.$F < Cl > Br > I$
C.$F > Br > Cl > I$
D.$I > Cl > Br > F$

Answer 1

We have to remember that the term electron gain enthalpy refers to the amount of energy that is released when an atom accepts the electron from any neutral isolated gaseous atom to form a negative gaseous ion (anion). It is measured in the unit of volts per atom or kilojoule per mole.

Complete step by step answer:
We know that the halogens have high negative electron gain enthalpy. The atoms of halogens gain stability by gaining electrons. They have a strong affinity to reach the stable state, noble gas state by accepting electrons.
Here, in this particular example we have four halogens 0- fluorine, chlorine, bromine and iodine.
If we look at fluorine, the electron gain enthalpy of fluorine is less negative than that of chlorine due to its comparatively small size.
If we look at chlorine, bromine and iodine, the electron gain enthalpy decreases as we go from chlorine to iodine. This is due to basic phenomena of electronegativity, it decreases as we go down in group (as the size of the atom increases).
Hence, the correct order of electron gain enthalpy is $F < Cl > Br > I$.
Hence, the correct answer is option B.

Note:
We have to remember that the electron gain enthalpy represents the energy involved in a reaction process. It also explains about the strength of the extra electron that gets bound to the gaseous atom. The more energy released in a chemical reaction, the more the electron gains enthalpy of the element. The reactions can be either exothermic or endothermic in nature.