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Electronegativity and Polarity

Learn about electronegativity, electron affinity, and polarity in chemistry. Explore the scale developed by Linus Pauling and how it affects bond types. Understand ionic, nonpolar covalent, and polar covalent bonds, along with examples and solubility properties. Discover intermolecular forces and physical properties of covalent compounds.

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Electronegativity and Polarity

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  1. Electronegativity and Polarity Section 9-5

  2. Electron affinity • Tendency of atom to accept electron • Usually increases as atomic numbers increase within period • Usually decreases as atomic number increases within a group

  3. Linus Pauling • Developed scale of electronegativity • Figure 9-15, pg 263 • Fluorine has the highest: 3.98 • Francium has the lowest: 0.7 • Noble gases are not given (0)

  4. Electron Affinity tells us… • Character and type of bond • Never completely ionic or covalent • Sharing is not always completely equal

  5. Ionic Bond • Large differences in electronegativity indicate that electrons are transferred

  6. Nonpolar covalent bonds • Difference in electron affinity of atoms involved is very small • Electrons shared fairly equally

  7. Identical Atoms • Difference in electronegativity is 0 • Electrons are shared equally.

  8. Polar Covalent Bonds • Unequal sharing • Electron tug-of-war • Stronger affinity = greater strength

  9. Differences • Less than 0.4 = nonpolar covalent bond • 0.4 – 1.7 = polar covalent bond • Greater than 1.7 = ionic bond

  10. Examples: • H and Br 2.20 and 2.96 = 0.76 polar covalent • C and O 2.55 and 3.44 = 0.89 polar covalent • Li and F 0.98 and 3.98 = 3.00 ionic bond

  11. Solubility of Polar Molecules • Like dissolves like • Polar (and ionic) compounds are soluble in polar substances • Nonpolar only soluble in non-polar substances

  12. Properties of Covalent Compounds • Van der Waals forces: weak forces of attraction between individual molecules

  13. Types of Intermolecular Forces • Nonpolar • Weak attraction • Dispersion or induced dipole • Polar • Stronger attraction • Dipole-dipole force • Hydrogen bond • Very strong • Between H and another dipole

  14. Physical properties • Melting/boiling points lower than ionic • Many are gases at room temp • Non-conductors of heat or electricity • Extremely hard *Due to the intermolecular forces!!

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