Electronegativity and Bond Polarity

Electronegativity is one of the most important concepts linking bonding to molecular properties. It determines whether a covalent bond is polar or non-polar, and whether a molecule as a whole has a dipole moment. Understanding polarity is essential for predicting solubility, intermolecular forces, and physical properties.

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What Is Electronegativity?

Electronegativity is the ability of an atom to attract the bonding pair of electrons in a covalent bond towards itself. It was first quantified by Linus Pauling, who developed the Pauling electronegativity scale.

Key trends in the periodic table:

• Electronegativity increases across a period (left to right). Across a period, nuclear charge increases while shielding remains roughly constant. The bonding electrons are more strongly attracted to atoms with greater effective nuclear charge.
• Electronegativity decreases down a group. Down a group, the atomic radius increases and there are more inner electron shells shielding the nucleus. The bonding electrons are further from the nucleus and experience less attraction.
• Fluorine is the most electronegative element (4.0 on the Pauling scale), followed by oxygen (3.5), nitrogen (3.0), and chlorine (3.0).

Noble gases are generally not assigned electronegativity values because they do not typically form covalent bonds.

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