REDOX REACTIONS
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
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
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
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
Memory Tip LEO (the lion says) GER LEO: Lose Electrons Oxidation GER: Gain Electrons Reduction
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
TRY THIS Na + + Cl - NaCl Which atom is oxidized? Na Which atom is the oxidizing agent? Cl
TRY THIS Iron(III) oxide lost its oxygens – it has been reduced. Oxidizing agent Carbon monoxide gains oxygen – it has been oxidized. Reducing agent.
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
EXAMPLE
OTHER EXAMPLES Oxidation: Bleaching Corrosion Antiseptics Reduction: Photosynthesis Antioxidants (prevent oxidation by reducing) Photography
Reading Read page 114 to120 of textbook