Question

Give reason chlorine shows greater electron gain enthalpy than fluorine

Answer 1

We know that as we go down a group in the periodic table the electron affinity decreases.. [As we go down a group no. of shells increases=>atomic size increases=>nuclear pull on outside electron decreases.]

So as chlorine is below fluorine in periodic table should have E.A less than fluorine.
But that is not the case. Instead chlorine has E.A greater than fluorine.

Why??????????

This is because fluorine due to its small atomic size has an inter electronic repulsion[repulsion between the electrons in fluorine] in it. So this repulsive force results in a weak force on the outer most electrons.

On the other hand chlorine being larger in size do not experience inter electronic repulsion thus have greater E.A than fluorine.
Hope this helps: )

Answer 2

it is because fluorine has a very small size so electron density is high as a result added electron experience electronic repulsion and to minimise electronic repulsion some amount of energy is absorbed.So,it happens .

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