please explain why chlorine is more electonegative than flourine however in p-block metallic character increses? please don't repeat the same answer.

Please note that fluorine is indeed more electronegative than chlorine. In fact, fluorine is the most electronegative element in the periodic table. It is much smaller in size than chlorine and has a greater tendency to attract electrons than chlorine. 

However, the electron gain enthalpy of chlorine is more negative than fluorine. This is because fluorine is smaller in size than chlorine. Thus the extent of electron-electron repulsion would be more in fluorine than in chlorine. Because of this, the incoming electron would face more repulsion in fluorine than in chlorine. Chlorine on the other hand being larger in size, accepts the electron more readily than fluorine.

In other words, the chloride ion is formed more easily than the fluoride ion. 

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Electron affinity of an element is the energy released from the atom when an electron is added to its valence shell. because the energy is released, electron affinity is always a negative value.


Size of F atom is too small and its electrons are too close to each other that there is high inter electronic repulsion among the electrons of F.

Any upcoming electron into the atom feels a large amount of repulsion by the electronic cloud of F and thus its not so easy for the electron to enter into the atom. thus the electron gain enthalpy of F less than the expected value. in fact it is even less than the electron affinity of Cl atom

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 Sorry, wrong answer posted by me! I thought ur asking for electron gain enthalpy.

But I think ur question is wrong! coz its the other way round. F is more elctronegative than Cl.

The reason is as follows:

2 factors affect the electronegativity of an element - nuclear charge and radius of the atom.
If the element has a large nuclear charge it will attract electrons to it more readily than one with a small nuclear charge.
If the element is small then the effect of the pull from the nucleus will be greater (due to physical distance between the nucleus and the outside of the atom and the effect of electron shielding - shells of electrons reducing the 'pulling' power of the nucleus)
As we go across a period the atomic radii of the atoms decreases. As we go down a group the atomic radii of the atom increases (even though the nuclear charge also increases, the atomic radii increases to a greater extent which practically cancels out the effect of the increased nuclear charge)

Therefore the most electronegative element is Fluorine, followed by Oxygen, Nitrogen and Chlorine:-


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