Electronegativity

Definition

Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. It is a fundamental concept in understanding the nature and strength of chemical bonds, as well as predicting the polarity and reactivity of molecules.

5 Must Know Facts For Your Next Test

1. Electronegativity is a periodic trend, with electronegativity values generally increasing from left to right across the periodic table and decreasing from top to bottom.
2. Differences in electronegativity between bonded atoms lead to the formation of polar covalent bonds, which have a partial positive and partial negative charge.
3. The polarity of a molecule, as measured by its dipole moment, is directly related to the differences in electronegativity between the atoms involved in the chemical bonds.
4. Resonance structures can help stabilize molecules by redistributing electron density and minimizing differences in electronegativity between atoms.
5. Electronegativity differences are a key factor in determining the strength and stability of acids and bases, as well as the reactivity of organic compounds.

Review Questions

• Explain how electronegativity differences lead to the formation of polar covalent bonds and the resulting dipole moments in molecules.
  • When atoms with different electronegativities form a covalent bond, the shared electrons are not equally distributed between the atoms. The atom with higher electronegativity will have a greater pull on the shared electrons, resulting in a partial negative charge on that atom and a partial positive charge on the other. This unequal distribution of charge creates a dipole moment, which is a measure of the polarity of the molecule. The magnitude of the dipole moment is directly proportional to the difference in electronegativity between the bonded atoms.
• Describe how resonance structures can help stabilize molecules by minimizing differences in electronegativity between atoms.
  • Resonance occurs when a molecule can be represented by multiple valid Lewis structures, which helps to distribute the electron density more evenly throughout the molecule. By allowing the electrons to be shared across multiple bonds and atoms, resonance can minimize the differences in electronegativity between the atoms involved. This stabilizes the molecule and reduces the overall polarity, making the molecule less reactive. Resonance is an important factor in understanding the stability and reactivity of organic compounds, such as those found in the chemistry of nitriles and the acidity of certain functional groups.
• Analyze how electronegativity differences affect the strength and stability of acids and bases, as well as the reactivity of organic compounds.
  • The electronegativity difference between an acid and a base is a key factor in determining the strength of the acid-base interaction. Stronger acids have a higher electronegativity than the base they are reacting with, allowing them to more effectively withdraw electrons and stabilize the conjugate base. This results in a more stable acid-base pair and a stronger acid. Similarly, the electronegativity of substituents on organic compounds can influence the acidity or basicity of the molecule, as well as its overall reactivity. Electron-withdrawing groups with high electronegativity can stabilize negative charges, increasing acidity, while electron-donating groups can have the opposite effect. Understanding these electronegativity-driven trends is crucial for predicting and explaining the behavior of organic reactions.

Related terms

Polar Covalent Bond: A chemical bond in which the shared electrons are not equally distributed between the bonded atoms, resulting in a partial positive and partial negative charge.

Dipole Moment:

The measure of the separation of charge within a polar molecule, which determines the overall polarity and reactivity of the molecule.

Resonance:

The ability of a molecule to be represented by multiple valid Lewis structures, which helps to stabilize the molecule and distribute electron density.