elektronegative

Electronegativity is a chemical property describing the tendency of an atom to attract electron density toward itself when forming a chemical bond. It is a contextual property, arising from an atom’s environment in a molecule, and is not measured as a direct property of an isolated atom in vacuum. Higher electronegativity indicates a stronger pull on shared electrons in bonds.

The most widely used scale is the Pauling scale, where fluorine is assigned a value of about 4.0, the highest among elements. Other elements are ranked relative to this reference. Electronegativity can also be estimated by different methods: the Mulliken scale defines it as the average of an atom’s ionization energy and electron affinity (in electronvolts), while scales such as Allred–Rochow relate it to effective nuclear charge and covalent radius.

Periodic trends show that electronegativity generally increases across a period from left to right and decreases down a group. Nonmetals typically have higher electronegativities than metals; elements like oxygen and fluorine are among the most electronegative. On common scales, hydrogen is around 2.1, carbon about 2.5, nitrogen about 3.0, oxygen about 3.4, and chlorine around 3.0–3.2. Noble gases are usually not assigned electronegativity values on many scales because they rarely form the kind of bonds used to define the concept.

Differences in electronegativity between bonded atoms influence bond polarity and character. Large differences tend to yield ionic bonds, moderate differences yield polar covalent bonds, and small differences yield nonpolar covalent bonds. While exact thresholds vary, differences greater than roughly 1.7 are often associated with ionic character, and differences below about 0.4 with nonpolar covalent character.

Electronegativity aids in predicting molecular polarity, reactivity, acidity, and the stability of reactive intermediates, making it a foundational concept in inorganic and organic chemistry.