Oxidation-Reduction Reactions: “REDOX REACTIONS”
- One or more electrons are transferred
o Examples: Photosynthesis and some combustion of hydrocarbons
- Even though none of the reactants or products in this reaction is ionic, the reaction is still
assumed to involve a transfer of electrons from carbon to oxygen.
Oxidation States (Oxidation numbers): Helps us to keep track of electrons in oxidation-reduction
- Oxidation states of the atoms in a covalent compound are defined as the imaginary charges
the atoms would have if the shared electrons were divided equally between identical atoms bonded
to each other, or for different atoms, were all assigned to the atom in each bond that has the greater
attractions for electrons.
- Remember what electrons do in covalent bonds?
- The oxidation states of atoms in covalent compounds are obtained by arbitrarily assigning
the electron to particular atoms.
o Example: H2O
Oxygen is more electronegative (electron hungry).
Oxygen has “taken 2 electrons (one from each hydrogen, therefore it has a
-2 oxidation state and each hydrogen has a +1 oxidation state)
* View Table 4.2 for the rule for assigning oxidation states
Assign oxidation numbers to each atom in the following compounds or ions. Show your work!!!!
g. SO3 2-
j. NO3 -
The Characteristics of Oxidation-Reduction Reactions:
- They are characterized by a transfer of electrons
o Oxidation = increase in oxidation state = loss of electrons
o Reduction = decrease in oxidation state = gain of electrons
- What ever species is reduced is considered the oxidizing agent
o (electron acceptor)
- Whatever species is oxidized is considered the reducing agent
o (electron donor)
Complete Page 182- 183 # 54, 56, & 58