Topic no 6

Electronegativity

                Electronegativity is a measure of an atom's ability to attract shared electrons towards itself in a covalent bond. It's a crucial property in understanding the nature of chemical bonds, particularly covalent bonds.

Trends in Electronegativity:


·         Across a Period:

o    Increases: 

                    Electronegativity generally increases from left to right across a period. As atomic size decreases and effective nuclear charge increases, the nucleus has a stronger attraction for electrons, including shared electrons in covalent bonds.

·         Down a Group:

o    Decreases: 

                    Electronegativity generally decreases from top to bottom within a group. As atomic size increases, the shielding effect of inner electrons weakens the attraction between the nucleus and shared electrons.

Examples:

·         Group 17 elements (halogens): Halogens have high electronegativities, making them highly electronegative elements. This means they strongly attract shared electrons in covalent bonds, often forming polar covalent bonds or ionic bonds.

·         Group 1 elements (alkali metals): Alkali metals have low electronegativities, making them electropositive elements. They are less likely to attract shared electrons and often form ionic bonds by losing electrons.

Factors affecting electronegativity:


·         Atomic size: 

                    Smaller atoms have higher electronegativities due to stronger nuclear attraction.

·         Shielding effect: 

                    The presence of inner electrons can shield the nucleus from shared electrons, reducing the attraction.

·         Electron configuration: 

                    Atoms with half-filled or completely filled subshells may have slightly higher electronegativities due to the stability associated with these configurations.

In summary: 

            Electronegativity is a measure of an atom's ability to attract shared electrons in a covalent bond. It increases across a period and decreases down a group, reflecting trends in atomic size and shielding effects. Electronegativity is crucial for understanding the polarity of covalent bonds and the nature of chemical interactions between atoms.