Question

The electron affinity values for the halogens show the following trends?

• A. $\mathrm{F}<\mathrm{Cl}>\mathrm{Br}<\mathrm{I}$
• B. $\mathrm{F}<\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$
• C. $\mathrm{F}<\mathrm{Cl}<\mathrm{Br}<\mathrm{I}$
• D. $\mathrm{F}>\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$

Answer 1

The correct option is B

$\mathrm{F}<\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$

The explanation for the correct option:

Option(B):$\mathrm{F}<\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$

• Electron affinity of an atom or molecule is basically known as the energy released when an electron gets added to a neutral atom or molecule in its gaseous state forming a negative ion.
• As the atomic size increases down the group, the electron affinity mostly tends to decrease down the group as the electron will not be as attracted to the nucleus with the increase in the size, which results in a low electron affinity.
• In the case of halogens, fluorine tends to have a lower electron affinity than chlorine, which is due to the small size of fluorine as compared to chlorine.
• Due to this, the electron affinity values for the halogens show the following trends, given as:$\mathrm{F}<\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$

The explanation for the incorrect option:

Option(A):$\mathrm{F}<\mathrm{Cl}>\mathrm{Br}<\mathrm{I}$

• The electron affinity tends to progressively decrease down the group of halogens with the respective increase in the size of the halogens.
• Hence, the given option does not represent the correct concept.

Option(C):$\mathrm{F}<\mathrm{Cl}<\mathrm{Br}<\mathrm{I}$

• With the progressive increase in the size of the halogens, the electron affinity tends to decrease respectively down the group of halogens.
• Thus, the given option is the incorrect one.

Option(D):$\mathrm{F}>\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$

• Due to the small size of fluorine as compared to chlorine, fluorine has a lower electron affinity than chlorine, which then progressively decreases as we go down the group of halogens.
• Hence, the given option does not coincide with the correct concept.

Hence, the electron affinity values for the halogens show the following trends:$\mathrm{F}<\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$, option (B) is the correct answer.