Question

Why bromine has low electron gain enthalpy than chlorine and flourine

Answer 1

Fluorine, though higher than chlorine in the periodic table, has a very small atomic size. This makes the fluoride anion so formed unstable (highly reactive) due to a very high charge/mass ratio.
Where as chlorine just has the perfect size.
As a result, fluorine has an electron gain enthalpy less than that of Chlorine.


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Answer 2

Explanation:

Electron gain enthalpy of F is less negative than that of Cl because when an electron is added to F,the added electron goes to the smaller n=2 quantam level and suffers repulsion from other electons present in this level. In case of Cl,the added electron goes to the larger n=3 quantam level and suffers much less repulsion from other electron.

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