[arvind1990]

which is more electronegative Helium or fluorine.Can anyone explain me in detail.

[Dan]

Electronegativity is basically a measure of how much "electron attracting power" an atom/ion has.

I find that the Mulliken electronegativity is a good scale to use for this explanation. Now, the Mulliken scale of electronegativity is obtained by averaging ionisation energy and electron affinity.

I'm not going to give you the answer, but in light of what I wrote above can you work out which has a greater electronegativity?

[cuongt]

all ive learnt is that fluorine has the most electronegativity in the periodic table  .
wat i dont understand is how helium neon and argon dont have an electronegativity number

[Yggdrasil]

To add to Dan's description, electronegativity is a measure to the "electron attracting power" of an atom when bonded to another atom.  Since He, Ne, and Ar don't form bonds with other molecules (well, it's questionable whether Ar can form bonds or not), the concept of electronegativity really doesn't apply to them.

[skyglow1]

He, Ne and Ar don't readily form compounds, so its difficult to measure their electronegativities.

[cuongt]

thanks sky glow

[arvind1990]

 
  But according to mulliken scale Helium has got the highest electronegativity(4.6) as Helium(noble gases) has  the highest IE among all the elements.Inspite of noble gases having electron affinity zero since they have got the highest IE,it is obvious that they have the highest Electro Negativity.
If so, What is the oxidation state of fluorine in the compound HHeF(a metastable comound which disintegrates by passing it thro' the energy barriers).

[tamim83]

For an excited state He atom, you can actually measure the electronegativity aparently.  I talked to my research advisor about this, metastable (excited state) noble gases are part of our research.  He said that a metastable helium atom would have an electronegativity similar to Li (lithium).  So flourine would then have an oxidation number of negative one still. 

Just wanted to say that this is a pretty advanced topic for a high school chem. course.  You must be pretty darn advanced for your grade level, or are you not a high schooler?  Either way, great question 

[arvind1990]

         I am an IIT aspirant. this question made me think too much.
You have talked abt the excited state of He. But what about He in the ground state.
Can anyone find a solution for it. (or) can anyone guide me to any of the website where I
can find a solution for it. I would be be very grateful.

[LordHokage]

Well, from what I have learned in my Chem 11 class, like those above me have stated, electronegativity is the measure of an atom's affinity for acquiring electrons.

So by looking at the periodic table, you can conclude that Fluorine is the most electronegative element. Helium is a noble gas, which means that the orbital(s) is full. The s-orbital requires two electrons and it has just that. Since it is full, it doesn't have an attraction for other electrons of an element.

Generally speaking, you can use the periodic trends to help you with further questions like these.

We know that as the atomic number increases, the number of protons will too, so it will have a higher attraction for electrons, ie. a higher electronegativity. And as the atomic number increases down the group, we know that the atomic radii increases, because the electrons are at higher orbitals, making them farther away from the nucleus of the atom. The shielding in between the electrons reduce the attraction from the protons in the nucleus resulting in a weaker electronegativity. So from this, you can conclude that fluorine is the most electronegative element.

Hope this answers your question!