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Electronegativity and Polarity

Electronegativity and Polarity. Chem 332 – O’Dette. How do you determine the polarity of a molecule?. Based on polarity of bonds and shape of the molecule Depends on the electronegativity of the elements in the molecule. What is electronegativity?.

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Electronegativity and Polarity

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  1. Electronegativity and Polarity Chem 332 – O’Dette

  2. How do you determine the polarity of a molecule? • Based on polarity of bonds and shape of the molecule • Depends on the electronegativity of the elements in the molecule

  3. What is electronegativity? • Ability of an element to attract electrons • Look up the values in a table • “Tug of War”

  4. Polarity of Bonds 0 – 0.4 Nonpolar Covalent Polar Covalent 0.5 – 1.8 Ionic 1.9 – 3.3

  5. Polarity of Covalent Bonds • Nonpolar Covalent • What happens with the electrons in a nonpolar covalent bond? • Electrons are shared equally between the atoms • EX: H2 H : H H – H Electronegativity H = 2.1 H = 2.1 Difference = 0

  6. Polarity of Covalent Bonds • Polar Covalent • What happens with the electrons in a polar covalent bond? • Electrons are shared unequally between the atoms • EX: HBr : H : Br H – Br: : Electronegativity H = 2.1 Br = 2.8 Difference = 0.7 Br has a stronger pull on the electrons

  7. Polarity of Molecules • Is it possible to have a compound with polar bonds in it but for the compound itself to be nonpolar? NH3 vs. CO2 H – N – H : O = C = O : : : : H Electronegativity N= 3 H = 2.1 Difference = 0.9 Electronegativity C= 2.5 O = 3.5 Difference = 1 Polar Molecule Nonpolar Molecule

  8. Polarity of Molecules • Even if the bonds between atoms are polar, the overall molecule polarity is nonpolar if • There are no lone pairs on central atom • Elements surrounding central atom are the same

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