1. REDOX REACTIONS

2. BONDING Occurs in order for atoms to become stable Atoms need a full outer shell to be stable Atoms may form :  Ionic bonds: gain/lose e-  Covalent bonds: sharing electrons  Includes diatomic molecules – HOFBrINCl  Hydrogen bonds: due to polarity of molecules

3. REDOX REACTIONS Reduction – Oxidation Reaction Most important energy changes occur in living organisms via redox reactions (rxns) Involves the transfer of electrons between two atoms  One atom is oxidized  One atom is reduced They always occur together

4. REDUCTION Electrons are gained Charge is negative hence the term ‘reduced’ Energy is absorbed – an ENDERGONIC rxn Can be recognized in 3 ways:  1) removal of an oxygen  2) gaining a hydrogen  3) gaining an electron

5. OXIDATION Electrons are removed or lost Molecule becomes less negative Releases energy – an EXERGONIC rxn Can be recognized in 3 ways:  Oxygen is added  Hydrogen is removed  Electron is removed  Does not necessarily involve oxygen

6. Memory Tip LEO (the lion says) GER LEO: Lose Electrons  Oxidation GER: Gain Electrons  Reduction

7. Redox Terminology Electron Donor:  one that loses e- Electron Acceptor:  one that gains e- Oxidizing Agent:  one that is reduced but causes another atom to be oxidized Reducing Agent:  one that is oxidized but causes another atom to be reduced

9. TRY THIS Na + + Cl -  NaCl Which atom is oxidized?  Na Which atom is the oxidizing agent?  Cl

10. TRY THIS Iron(III) oxide lost its oxygens – it has been reduced. Oxidizing agent Carbon monoxide gains oxygen – it has been oxidized. Reducing agent.

11. Role of Electronegativity In order to oxidize an atom, energy is needed to force the electrons to leave their parent atom Substances with a high electronegativity do not let their e- go easily and therefore require more energy to be oxidized than those with low electronegavities

12. EXAMPLE

13. OTHER EXAMPLES Oxidation:  Bleaching  Corrosion  Antiseptics Reduction:  Photosynthesis  Antioxidants (prevent oxidation by reducing)  Photography

14. Reading Read page 114 to120 of textbook