1. Strength of Covalent Bonding Chapter 8.8 LeoPeter

2. Strengths of Covalent Bonds The stability of a molecule is dependent on the strength of the covalent bondsThe stability of a molecule is dependent on the strength of the covalent bonds –The bond strength is determined by how much energy is required to break the bond –Less energy required to break the bond = Weaker bond –The more bonds between two atoms, the closer they are together The closer the atoms are together, the stronger the bondingThe closer the atoms are together, the stronger the bonding Ex:http://wps.prenhall.com/esm_brown_chemistry_9/2/667/170 886.cw/index.htmlEx:http://wps.prenhall.com/esm_brown_chemistry_9/2/667/170 886.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistry_9/2/667/170 886.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistry_9/2/667/170 886.cw/index.html

3. Bond Enthalpy and Enthalpies of Reactions Bond enthalpy is the energy needed to break the bond between atomsBond enthalpy is the energy needed to break the bond between atoms The more bonds, the higher the bond enthalpyThe more bonds, the higher the bond enthalpy When a bond is made – exothermicWhen a bond is made – exothermic When a bond is broken – endothermicWhen a bond is broken – endothermic

4. Enthalpies of Reactions Cl-Cl bond energy = 242 kJ/mol H-H bond energy = 436 kJ/mol H-Cl bond energy = 431 kJ/molCl-Cl bond energy = 242 kJ/mol H-H bond energy = 436 kJ/mol H-Cl bond energy = 431 kJ/mol

5. Bond Enthalpy Bond enthalpy = the enthalpy change = ΔH of a mole of single bondsBond enthalpy = the enthalpy change = ΔH of a mole of single bonds –Ex: http://wps.prenhall.com/esm_brown_chemistry_9/ 2/666/170666.cw/index.html http://wps.prenhall.com/esm_brown_chemistry_9/ 2/666/170666.cw/index.html http://wps.prenhall.com/esm_brown_chemistry_9/ 2/666/170666.cw/index.html

6. Bond Enthalpy and Bond Length Bond length - the distance between the nuclei of the atoms involved in the bondBond length - the distance between the nuclei of the atoms involved in the bond With an increase in the number of bonds between atoms, the bond enthalpy increases and the bond length decreasesWith an increase in the number of bonds between atoms, the bond enthalpy increases and the bond length decreases The bond length decreases because the atoms are being held closer togetherThe bond length decreases because the atoms are being held closer together

7. Work Cited Brown, LeMay, Bursten, Chemistry: The Central Science, Upper Saddle River, New Jersey: Pearson Education Inc., 2003 http://www.simplechemconcepts.com/chemistr y-question-energy-changes-exoendo-bond- energy/http://www.simplechemconcepts.com/chemistr y-question-energy-changes-exoendo-bond- energy/http://www.simplechemconcepts.com/chemistr y-question-energy-changes-exoendo-bond- energy/http://www.simplechemconcepts.com/chemistr y-question-energy-changes-exoendo-bond- energy/ http://wps.prenhall.com/esm_brown_chemistr y_9/2/666/170666.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistr y_9/2/666/170666.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistr y_9/2/666/170666.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistr y_9/2/666/170666.cw/index.html http://wps.prenhall.com/esm_brown_chemistr y_9/2/667/170886.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistr y_9/2/667/170886.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistr y_9/2/667/170886.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistr y_9/2/667/170886.cw/index.html