Question

Fluorine has the highest electronegativity among the $n{s}^{2}n{p}^5$ group on the Pauling scale, but the electron affinity of fluorine is less than that of chlorine because-

• A. The atomic number of fluorine is less than that of chlorine.
• B. Fluorine being the first member of the family behaves in an unusual manner.
• C. Chlorine can accommodate an electron better than fluorine by utilizing its vacant 3d=orbital.
• D. Small size, high electron density and an increased electron repulsion makes addition of an electron to fluorine less favourable than that in the case of chlorine.

Answer 1

The correct option is D

Small size, high electron density and an increased electron repulsion makes addition of an electron to fluorine less favourable than that in the case of chlorine.

We know that atomic size of Flourine is smaller than chlorine.

$⟶$ Flourine already has 7 electrons in valence shell. Therefore if we will add one more electron, electrons present in the valence shell will repel that incoming electron because of the smaller size and high electron density.

Chlorine is larger in size and have 7 electrons in valence shell. Therefore it has less electron density and there will be less electron repulsions.

Therefore, because of small size, high electron density and increased electron repulsion, addition of an electron is less favourable in case of Flourine than Chlorine.

$\Rightarrow$ Cl > F [EA]