Jason Qian Jaemo Lee John Seo Electronegativity Jason Qian Jaemo Lee John Seo

Definition Electronegativity is a measure of the ability of an atom in a chemical compound to attract an electron from another atom in the compound.

Quick Facts Electronegativity cannot be directly measured; it must be calculated from other atomic or molecular properties. Most common scale of measurement for electronegativity is the Pauling scale. The Pauling scale ranges from 0.7 to 4.0 Hydrogen is approximately 2.2 Pauling units

The Periodic Trends In general, electronegativity increases from bottom to top in a column and left to right across a group. So the most bottom left element, Cesium, is the least electronegative. The most top right element, Fluorine, is the most electronegative.

The Shielding Effect Electronegativity depends on the Shielding Effect As more energy levels are added, the electrons of that level are repelled by the electrons between the protons and the electrons of the highest energy level. As you move towards the right of the periodic table, the number of protons increases while keeping the energy levels constant, so a larger attractive force reduces shielding As you move down a group, more energy levels are added, thus strengthening the shielding effect, which decreases the attraction between the outer electrons and the nucleus

Exceptions Does not include noble gases because they all have 8 valence electrons, causing them to be very stable. They are neither electronegative or electropositive. Gallium and germanium have higher electronegativities than aluminum and silicon because of the missing d-block electrons. Elements of the fourth period have very small atomic radii. This is because the electrons in the 3d orbital are not effective at “shielding” the increased positive charge. Smaller atomic size usually indicates a higher electronegativity.