Elektronegativität

Elektronegativität is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (a bonding pair) towards itself. This attraction arises from the electrostatic force between the positively charged nucleus of an atom and the negatively charged electrons. Atoms with higher electronegativity exert a stronger pull on bonding electrons.

The concept of electronegativity was first quantified by Linus Pauling in 1935, and his scale remains the most widely used. On the Pauling scale, fluorine is the most electronegative element with a value of 3.98, while cesium and francium are among the least electronegative with values around 0.7. Electronegativity generally increases across a period in the periodic table and decreases down a group. This trend is related to atomic size and nuclear charge. Smaller atoms with a greater effective nuclear charge tend to be more electronegative.

The difference in electronegativity between two bonded atoms determines the polarity of the chemical bond. If the electronegativity difference is large, the bond is considered ionic, where electrons are essentially transferred from the less electronegative atom to the more electronegative atom. If the difference is small, the bond is covalent, and electrons are shared. A polar covalent bond occurs when there is a moderate electronegativity difference, resulting in an unequal sharing of electrons and the formation of partial positive and partial negative charges on the atoms. This property is crucial for understanding chemical reactivity, molecular structure, and intermolecular forces.