BackElectronegativity, Polarity, and Chemical Bond Classification
Study Guide - Smart Notes
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Electronegativity
Definition and Measurement
Electronegativity (EN) is a measure of an atom's ability to attract electrons in a chemical bond. The concept was introduced by Linus Pauling in 1932, who assigned electronegativity values to elements.
Electronegativity values are dimensionless numbers that help predict bond type and polarity.
Higher electronegativity means a stronger pull on shared electrons.
Periodic Trend of Electronegativity
Electronegativity values show predictable trends across the periodic table:
Electronegativity increases from left to right across a period.
Electronegativity increases from bottom to top within a group.
Fluorine (F) is the most electronegative element.
Example: The most electronegative alkaline earth metal is Be (beryllium).
Bond Polarity and Dipole Moment
Polarity in Chemical Bonds
Polarity arises when atoms in a bond have different electronegativities, resulting in unequal sharing of electrons.
A difference in electronegativity greater than 0.4 is considered significant.
The greater the difference in electronegativity, the more polar the bond.
A dipole moment is created when electrons are pulled toward the more electronegative atom, resulting in partial charges.
Example: The difference in electronegativity between carbon and fluorine is 1.5.
Chemical Bond Classification
Types of Chemical Bonds Based on Electronegativity Difference
The type of chemical bond formed between two atoms depends on the difference in their electronegativities:
Electronegativity Difference | Bond Type | Bond Illustration |
|---|---|---|
Zero (0.0) | Pure covalent (nonpolar) | Br–Br, H–H |
Small (0.1–0.4) | Nonpolar covalent | C–H |
Intermediate (0.5–1.7) | Polar covalent | Cl–H |
Large (>1.7) | Ionic | Na–F |
Example: The most polar bond among S–Se, S–H, Cl–F, and S–O is Cl–F.
Practice Questions and Applications
Electronegativity Order
Arrange the following elements in order of decreasing electronegativity: P, Na, N, Al.
Order: N > P > Al > Na
Greatest Electronegativity Difference
Between which two elements is the difference in electronegativity the greatest?
Answer: C and Si
Bond Type Identification
Which of the following correctly identifies the chemical bond between two bromine atoms?
Answer: Polar Covalent
Key Terms and Concepts
Electronegativity (EN): Ability of an atom to attract electrons in a bond.
Polarity: Unequal sharing of electrons due to electronegativity difference.
Dipole Moment: A measure of bond polarity; points toward the more electronegative atom.
Covalent Bond: Electrons are shared between atoms.
Ionic Bond: Electrons are transferred from one atom to another.
Formulas and Equations
Electronegativity Difference:
Bond Classification by Electronegativity Difference:
Pure Covalent:
Nonpolar Covalent:
Polar Covalent:
Ionic:
Additional info: The notes provide foundational concepts for understanding chemical bonding in GOB Chemistry, including how electronegativity differences determine bond type and polarity, and how to use the periodic table to predict these properties.
