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Bond Strength, Bond Length, and Bond Energy

Bond Strength, Bond Length, and Bond Energy. Bond Energy. The energy required to break the bond between two covalently bonded atoms- bond dissociation energy Unit is kJ/mole ( kiloJoule per mole) A large bond dissociation energy indicates a strong covalent bond. Bond Energy/Bond Length.

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Bond Strength, Bond Length, and Bond Energy

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  1. Bond Strength, Bond Length, and Bond Energy

  2. Bond Energy • The energy required to break the bond between two covalently bonded atoms- bonddissociation energy • Unit is kJ/mole (kiloJoule per mole) • A large bond dissociation energy indicates a strong covalent bond

  3. Bond Energy/Bond Length • As the number of bonds between two atoms increases the bond length decreases and the bond energy increases • Electron density between atoms increases the nuclear attraction

  4. Bond energy Bond length • C-C 347 kJ/mol 154 pm • C=C 657 kJ/mol 134 pm • C=C 908 kJ/mol 120 pm

  5. Bond Energy/Bond Length

  6. Bond Energy/Bond Length • The size of the atom makes a difference! • As the atomic radii of bonding atoms increases, • The bond length increases bond energy decreases

  7. Bond Length/Bond Strength

  8. Bond length • Measured using X-ray crystallography • Positions of atoms can be identified based on the diffraction of Xrays by a crystal • Infrared spectroscopy • Uses the frequency of vibration of molecule and the wavelength of laser can determine distance between atoms Single bond is longest, triple bond is shortest

  9. Resonance • Resonance structure- draw two or more valid Lewis structures for the same molecule • The structure of a molecule is an average of all of the equivalent resonance structures • Proven by Xray diffraction • Ozone O3

  10. Resonance- Effective Bonds • Effective bonds explain why the bonds are the same length • Effective bonds = #of bonds / # of outer atoms

  11. Effective bonds = 3/2 = 1.5

  12. Effective bonds = 4/3 = 1.33

  13. Effective bonds = 4/3 = 1.33

  14. Ozone formation from oxygen molecules

  15. CFC’s

  16. how the ozone layer works and CFCs

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