Elektronegativitása

Elektronegativitása is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself in a covalent chemical bond. This property is not a directly measurable quantity but is rather a calculated value. It is a fundamental concept in understanding chemical bonding and predicting the polarity of molecules.

Several scales have been developed to quantify electronegativity, with the Pauling scale being the most widely used. On this scale, fluorine is assigned the highest electronegativity value of 4.0, while elements like cesium and francium have the lowest values, around 0.7. Generally, electronegativity increases across a period in the periodic table from left to right and decreases down a group. This trend is influenced by factors such as nuclear charge and atomic radius.

The difference in electronegativity between two bonded atoms is a key determinant of the type of bond formed. A large difference indicates a high likelihood of ionic bonding, where electrons are effectively transferred from the less electronegative atom to the more electronegative atom. A smaller difference suggests a polar covalent bond, where electrons are shared unequally, creating partial positive and negative charges on the atoms. When the electronegativity difference is very small or zero, the bond is considered nonpolar covalent, with electrons shared almost equally. Understanding electronegativity is crucial for predicting molecular geometry, reactivity, and physical properties like boiling point and solubility.