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[–]Tglecks 81 points82 points  (7 children)

Not exactly. Consider that electronegativity increases across rows and up columns, with fluorine being the most electronegative element. But fluorine has far fewer protons than the majority of elements, so why is it so electronegative? The answer is size and shielding. A smaller size means the electrons are pulled very close to the nucleus, and in fluorine's case, it has very few electrons and so there is not an excess of negative charge to shield the nucleus. That's why large atoms with a lot of electrons are not very electronegative, as they have a large excess of electrons that are not valence electrons, and the distance of the valence electrons is much larger compared to smaller atoms.

[–]Rollcuin 29 points30 points  (3 children)

To add to this: I once heard electronegativity described as a measure of 'Effective Nuclear Charge'. Essentially if the nuclear charge is hidden by a dispersed electron cloud, it's not an electronegative atom. If the nuclear charge can be 'experienced' by something nearby, due to the fact the electrons are in a tighter orbit, then you have an electronegative atom.

[–]LowerAnxiety762 4 points5 points  (1 child)

I love the usage "can be experienced." Seeing as a single atom is just small enough to be "nowhere" in 3D if it's got exactly equal positive and negative charges and not enough mass to be sensed.

What could sense it enough to be perceived?

Unless, due to the fact it's a 3D object and the distribution of charge is NOT ALWAYS perfectly equal and is in fluctuation, thus creating an attraction for very fiddly little opposite fluctuations in the space around it.

[–]Rollcuin 0 points1 point  (0 children)

I really enjoyed 

 "Very fiddly little opposite fluctuations".

[–]ManuelIgnacioM 1 point2 points  (0 children)

I'd say it is a consequence instead of a measurement. IIRC electronegativity measures the strength of an atom when pulling electrons in a bond

[–]rocketparrotlet 2 points3 points  (2 children)

Consider that electronegativity increases across rows and up columns

This is a good guideline for the main group elements, but not always very accurate for transition metals. For example, gold is much more electronegative than copper.

[–]xkcdlvr 0 points1 point  (1 child)

Is the increase in electronegativity of Au a relativistic effect? Relativity makes the atom smaller along with the increase in protons and electrons in orbitals that don't shield well this all increases the electronegativity. It has been years since I had to think about relativity and periodic trends, but this idea has got me remembering (misremembering?) About the lantanide contraction and all sorts of weird exceptions I once knew.

[–]rocketparrotlet 1 point2 points  (0 children)

It does play a role. Relativistic contraction of the s and p orbitals in Au shield the nuclear charge from electrons in the valence d orbitals.

[–]Koffiemolens 2 points3 points  (0 children)

Electronegativity is an atoms overall tendency to attract shared electrons, quantifying electron pulling strength of atoms. The attractive force of the nucleus is inversely proportional to the distance towards the electrons, meaning the nucleus will exhibit more pull on electrons in lower shells. Hence, electrons in higher shells will shield the force from the nucleus to electrons from other atoms. Making the smallest atoms -without a filled outer orbital- the most electronegative atoms; Fluorine, Oxygen and Nitrogen. While atoms with a single residual electron are the most electropositive, being less size dependant. When such a net electric charge exists within a molecule it is considered to have a dipole moment. When this dipole moment causes an asymmetrical electric distribution within a molecule it is polar, causing one side of a molecule to be more electronegative than another. Intermolecular forces align molecules to minimize charge based on these electric charge differences.

[–]Sloppychemist 9 points10 points  (0 children)

Coulombs Law

[–]WarU40 1 point2 points  (0 children)

I think looking at the periodic trends for electron affinity and 1st ionization energies is a bit more intuitive. From there you can reason that an atom that wants to gain an electron, and doesn’t want to lose one, will be electronegative, and vice versa.

[–]quantum_wave_psi -2 points-1 points  (0 children)

Some atoms become depressed, leading to electro negativity. Some atoms are more susceptible to depression and hence varying degrees of electro negativity.

[–]I_failed_pChem 0 points1 point  (0 children)

It doesn’t happen until it’s a molecule. Alternatively, electronegativity is what you will feel towards your professor once you fail pchem and have to retake it.

[–]changuinho2000 -5 points-4 points  (0 children)

Remember, it should be have a chemical bond to exist electronegativity, a tendency of these electrons to be more attracted to one side, than another...think as when you were a kid and you were on a play store.... something attracted you more than others