Question

Fluorine has the highest electronegativity among the ns2np5 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) f being the first member of the family behaves in an unusual manner
c) chlorine can accommodate an electron better than fluorine by utilising its vacant 3dorbital.
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 in isolated stage.

Answer 1

Though fluorine has the highest electronegativity, its electron affinity is lower than chlorine's due to increased electron-electron repulsion within its smaller n = 2 shell.

Step-by-step explanation:

The student's question is about the electron affinity (EA) of fluorine compared to chlorine, despite fluorine having the highest electronegativity. Fluorine has the highest electronegativity on the Pauling scale of all the elements, with a value of 4.0, which indicates its strong tendency to attract electrons. However, its electron affinity is less negative than that of chlorine.

The reason behind this is largely due to the small size of fluorine's n = 2 shell, which already houses a significant electron density, causing increased electron-electron repulsion. This repulsion makes the addition of an extra electron to a fluorine atom less favorable than to a chlorine atom, where the entering electron is added to the larger n = 3 shell, thereby experiencing less repulsion. Thus, the EA of fluorine is less negative at -322 kJ/mol compared to chlorine's -348 kJ/mol.