sähkönegatiivisuusarvo

Sähkönegatiivisuusarvo, often simply referred to as electronegativity, is a measure of the tendency of an atom to attract a bonding pair of electrons. This property is fundamental in understanding the nature of chemical bonds. When two atoms form a covalent bond, the electrons are shared between them. However, the sharing is rarely equal. The atom with a higher electronegativity will pull the shared electrons closer to itself.

The concept of electronegativity was first introduced by Linus Pauling in 1932, and he developed a scale to quantify it. On the Pauling scale, fluorine is the most electronegative element, with a value of 3.98, while cesium is one of the least electronegative, with a value of 0.79. Electronegativity generally increases across a period in the periodic table from left to right and decreases down a group. This trend is related to the nuclear charge and the distance of the valence electrons from the nucleus.

The difference in electronegativity between two bonded atoms determines the type of bond formed. If the difference is very small, the bond is considered nonpolar covalent, meaning the electrons are shared almost equally. A moderate difference results in a polar covalent bond, where electrons are shared unequally, creating partial positive and negative charges on the atoms. If the electronegativity difference is very large, the bond is considered ionic, where one atom essentially donates an electron to the other, forming ions. Understanding electronegativity is crucial for predicting molecular polarity, reactivity, and many other chemical properties.