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 OxidationGER: 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