Electronegativity

Posted on September 16, 2022 by Ayesha Abbasi

Electronegativity is the propensity of an atom in a molecule to draw the shared pair of electrons toward itself.

Because it is merely a propensity, this attribute has no dimensions.
It essentially represents the final consequence of atoms‘ propensities to attract electron pairs that form bonds in various elements.
On several scales, we quantify electronegativity. Linus Pauling created the most widely used scale.
The least electronegative element is cesium, which has a value of 0.7, and the most electronegative element is fluorine, which has a value of 4.0.
According to the importance of chemistry, electronegativity will be regarded as the primary factor in chemical bonding and is a significant quantity in defining the nature of bonds between elements.

Electronegativity of Elements: Periodic Trends

In the modern periodic chart, electronegativity increases across a period as we move from left to right because nuclear charge increases and atomic size decreases.
The periodic table’s electronegativity trend, for instance, is shown below for period 3.
As we travel down the group in the current periodic table, the atomic number rises.
Although the nuclear charge likewise rises, the effect of the rise is mitigated by the addition of one shell.
As we descend the group, electronegativity’s value drops.
For instance, the electronegativity value drops in the halogen group as we proceed from fluorine to astatine, as illustrated in the diagram below.
A general observation is that metals exhibit lower electronegativity values than non-metals.
As a result, the nature of metals and non-metals is electropositive and electronegative, respectively.
Due to their tiny size and greater electronegativity values, the elements in period two have different properties from the elements in their respective groups.

The second period’s features are similar to those of the following group in period three.
This is brought on by a little discrepancy in their electronegativities. As a result, a diagonal relationship develops.

The periodic table’s most electronegative element is fluorine. It has an electronegativity of 3.98.
The least electronegative element is cadmium. It has an electronegativity of 0.79.
Cesium is the most electropositive element because electro positivity is the exact opposite of electronegativity.
The most electronegative elements are those with the fewest inner electron shells between the positive nucleus and the valence electrons and the fewest required electrons to complete their valence shells.
Fluorine is the most electronegative of all the elements. It has a 4.0 electronegativity. Electronegativities for metals are less than 2.0.
With electronegativity values of 0.7, cesium (Cs) and francium (Fr) are the least electronegative elements.

Electronegativity’s Effect on Covalent Bonding

The electronegativities of the two bound atoms have a significant impact on the covalent bond’s strength (especially the difference in the electronegativities of the bonded atoms).
Homonuclear diatomic molecules have relatively “pure” covalent bonds because the bound atoms’ electronegativities match (resulting in the bonded pair of electrons being almost equidistant from the two bonded nuclei).
H2 molecules, Cl2 molecules, and O2 molecules are only a few examples of these covalent linkages in nature.
On the other hand, polarization often occurs in covalent bonds between two species with different electronegativities.
This happens as a result of the more electronegative atom drawing the bond pair of electrons closer to itself, which results in the development of a partial negative charge (often represented by the symbol -).
The more electropositive atom also develops a partial positive charge, represented by the symbol +, at the same moment. The polarity of the chemical connection is caused by these partial charges.