A Study on Electronegativity

The tendency for an atom of a certain chemical element to attract electron pairs (or electron density) while forming a chemical connection is referred to as electronegativity. The atomic number of an atom, and the distance between its valence electrons and the charged nucleus, define its electronegativity.  The more the associated electronegativity, the more electrons are attracted to an atom or a substituent group. The bond energy, as well as the sign and magnitude of a bond’s chemical polarity, that describes a bond along the continuous continuum from covalent to ionic bonding, can be computed using electronegativity. Electro-positivity describes an element’s inclination to give valence electrons and is the polar opposite of electronegativity.

A Study on Electronegativity

Electronegativity

Linus Pauling used the terminology “electronegativity” to describe the potential of an atom of an element to attract electron pairs while forming a chemical connection. Since different elements have varied powers to attract the bonding electron pair, the electron density in a covalent bond between two different elements is not shared equally.

Electronegativity is the tendency of an atom in a molecule to attract the equal pair of electrons to itself.

The electronegativity of an atom is a relative value in comparison to the electronegativity of the other atom with which it is bound. When one of the atoms in a bond is more electronegative than the other, the electron density of the bond will move slightly in favour of the more electronegative atom. Whenever 2 atoms or elements A and B are joined together, the electron pair will shift slightly towards A, giving A a slightly negative charge while B acquires a partial positive charge.

It is a dimensionless characteristic because it is only a propensity. It simply refers to the net outcome of an atom’s proclivity for attracting bond-forming electron pairs in various elements. We measure electronegativity on a variety of scales. The most widely used scale was designed by Linus Pauling. Fluorine is most electronegative element, with a value of 4.0, and cesium is least electronegative element, with a value of 0.7.

Factors Affecting Electronegativity

Size of an Atom

The value of electronegativity falls as the size of an atom grows larger. This is because electrons further out from the nucleus are exposed to less force of attraction.

Nuclear Charge

A higher electronegativity value refers to a larger nuclear charge. This happens since as nuclear charge rises, so does electron attraction.

Substituent Effect

The type of substituent linked to an atom determines its electronegativity. The carbon atom in CF3I, for instance, carries a larger positive charge than the carbon atom in CH3I. As a consequence, the C atom in CF3I has a higher electronegative charge than the C atom in CH3I. Substituents affect the electronegativity of an atom, which changes the atom’s chemical behaviour.

Periodic Trends in Element’s Electronegativities

As we move from left to right across a period in the traditional periodic table, the nuclear charge raises and the atomic size reduces, increasing the value of electronegativity.

Periodic Trend of Electronegativity

The atomic number rises as we move down the group in modern periodic table. The nuclear charge also rises, however the effect is lessened by the addition of one shell. As a consequence, the value of electronegativity decreases as we move down the group. As we move along the halogen group from fluorine to astatine, the electronegativity value decreases.

It is a truth that metals have a lower electronegativity than nonmetals. Metals are electropositive as a consequence, whereas non-metals are electronegative. Due to their small size and higher electronegativity value, Period 2 elements exhibit distinct characteristics than their respective group elements.

The second period’s characteristics are comparable to the third period’s next group. This could happen due to a slight difference in their electronegativities. A diagonal link is developed as an outcome.

Electronegativity’s Effect on Covalent Bonding

The strength of a covalent bond is mostly determined by the electronegativities of the two linked atoms (especially the difference in the electronegativities of the bonded atoms). Because the attached atoms’ electronegativities are the same, homonuclear diatomic molecules have relatively “pure” covalent bonds (resulting in the bonded pair of electrons being almost equidistant from the two bonded nuclei). Covalent bonding can be seen in H2 molecules, Cl2 molecules, and O2 molecules.

Electronegativity Series

The table below shows a list of elements in order of electronegativity, along with their atomic number, chemical symbol, and electronegativity value.

Conclusion

When only single bonds are present in the products and reactants, the Pauling concept of electronegativity leads to the conclusion that “combination of elements” reactions should always or nearly always be exothermic. The multiple bond energy of N2 and O2  is larger than 2 or 3 times that of the single bond energy. The ability to attract electrons is referred to as electronegativity. Electronegativity rises as the period progresses and as the group progresses. Dipoles are produced in covalent bonds due to electronegativity differences. Dipoles result in the formation of partial positive and partly negative endings.