Elektronegativitätsunterschiede

Electronegativity (Elektronegativität in German) is a chemical property that describes the ability of an atom within a molecule to attract bonding electrons toward itself. It is not a fixed attribute of an isolated atom; values depend on the atom’s environment, oxidation state, and the type of chemical bond involved. In practice, electronegativity is used to predict bond polarity and reactivity.

Several scales quantify electronegativity. The Pauling scale is the most widely used in introductory chemistry and assigns higher values to elements that attract electrons more strongly. On this scale, fluorine is the most electronegative element, with a value near 4, while elements such as cesium and francium have much lower values. The Mulliken scale defines electronegativity as the average of an atom’s ionization energy and electron affinity, typically expressed in energy units, and approximates the relative electronegativity across the periodic table. The Allred–Rochow scale relates electronegativity to the effective nuclear charge felt by bonding electrons, considering atomic size and covalent radii.

Periodic trends are characteristic: electronegativity generally increases across a period from left to right and decreases down a group. This trend reflects increasing effective nuclear charge and smaller atomic radii in the period, contrasted with shielding and larger size down a group. Noble gases are generally excluded from simple electronegativity comparisons because they rarely form bonds under standard conditions.

Applications include predicting bond polarity, acid-base behavior, ligand–metal interactions, and the likelihood of ionic versus covalent bonding. Limitations arise from context dependence, scale differences, and the fact that electronegativity is not defined for all species or environments.