The electronegativity is the ability of a atom for Attract electrons towards itself when combined with another atom in a Chemical bond . The greater the electronegativity, the greater the attraction capacity.
This trend of atoms is linked to your electroaffinity and his ionization potential . The most electronegative atoms are those that have a negative electronic affinity and high ionization potential, which allows them to conserve their electrons against the attraction that comes from outside and, in turn, attract the electrons of other atoms.
Electronegativity values are based on thermochemical data. The best known scale was proposed by the American chemist Linus Pauling (1901-1994), winner of Nobel Prize in Chemistry in 1954. In the pauling scale , the element of least electronegativity is the cesium with 0,7 , while the element with the highest electronegativity is the fluorine with 4 .
In this list or table we also find other elements that have low electronegativity such as potassium and rubidium with 0.82, barium and radius with 0.89 and sodium with 0.93.
On the contrary, among those who have it higher, in addition to the aforementioned fluoride, we encounter elements such as oxygen with 3.44, chlorine with 3.16, nitrogen with 3.04 and bromine with 2, 96.
When two atoms are joined whose electronegativities are very different from each other, a ionic bond . On the other hand, when atoms have similar electronegativities, a polar covalent bond , with the most electronegative atom remaining with the negative charge.
It should be noted that electronegativity is not a property atomic in the sense that it varies according to the context: it depends on the atom within the framework of a molecule . On the contrary, electro-affinity or electronic affinity is associated with an isolated atom (it is the Energy which releases an atom at its lowest energy level when it takes an electron and establishes a mononegative ion).
In addition to all of the above, we cannot ignore another series of relevant aspects of electronegativity, such as the following:
-The electronegativities of the elements come to increase from the bottom up within each group, while increasing from left to right within what are the different periods.
-According to Pauling, electronegativity depends on what the oxidation state is.
-In the scale of the aforementioned Pauling, the values become indexes, that is, they do not have unity.
-Other relevant figures who talked about electronegativity were A.L. Allred and E. G. Rochow. These came to make clear that for them that was the force of attraction that existed between an electron of bound atom and a nucleus.
-R. S. Mulliken also addressed the issue at hand. In his case, it became clear that the electronegativity of an element can be determined by carrying out the average electronic affinity and ionization energy of the valence electrons.