Question

Why is helium not the most electronegative elemnt?

Answer 1

It has no electronegativity because it is a noble gas.

Explanation:

Electronegativity describes an atoms relative tendency to attract a pair of electrons in a molecule. It can be described as a property of an atom within a molecule. As helium is a noble gas it will not react to form molecules and will thus not be in a situation where it would attract a pair of electrons within a molecule.

Answer 2

Because it has never formed `"He"_2`, so it did not have a Pauling electronegativity assigned to it. In fact, `"Ne"` is the most electronegative element!

---

There are, however, other electronegativity scales which do not depend on forming a homonuclear dimer, and `"He"` does have an electronegativity then.

Other scales are shown here:

A more modern electronegativity chart is shown here.

• A history of Pauling's derivation is shown here.

• You may want to read this article...

Answer 3

`"Why, are you serious?"`

Explanation:

By definition, `"electronegativity"` is defined as the ability of an atom involved in a chemical bond to polarize electron density towards itself. There are various scales, of which the Pauling scale was the earliest, and still very widely used.

I think you meant to ask why helium has the HIGHEST ionization energy of any element...i.e. the energy required for the reaction...

`X(g) + Delta rarr X^+(g) + e^(-)`...

...and such ionization reactions SPECIFY gaseous products and gaseous reactants. Now for helium, we gots a closed shell configuration...i.e. a nuclear charge of `+2`, and `"2 electrons"`, that are conceived to reside in the first electronic shell (the atomic radius is also smaller than that of the hydrogen atom, for which `Z=1`). And so let us interrogate some data...

And thus helium has the highest ionization energy, and forms NO conventional compounds. Why are the ionization energies of each alkali metal so disproportionately low?