Transcript 4c part 1 REDOX

REDOX
Oxidation-Reduction
Reactions
A redox reaction occurs when
electrons are transferred from one
substance to another
An Oxidizer – such as oxygen
 Is good at attracting electrons
 An oxidizer oxidizes something
 It takes the electrons from something
 When the oxidizer takes electrons from
something, the oxidizer gets reduced

A redox reaction occurs when
electrons are transferred from one
substance to another
A Reducer - such as lithium
 Is good at losing electrons
 A reducer reduces something
 It gives electrons to something
 When the reducer gives electrons to
something, the reducer gets oxidized

Oxidation Number – is used to rate
how well an atom takes or gives
electrons compared to other atoms
1. Each atom in a pure element has an
oxidation number of zero.
 2. For monatomic ions, the oxidation
number is equal to the charge on the ion.
 3. Fluorine always has an oxidation
number of -1 in compounds.

Oxidation Number – is used to rate
how well an atom takes or gives
electrons compared to other atoms
4. Cl, Br, and I always have oxidation
numbers of -1 in compounds, except when
with oxygen and fluorine.
 5. H is +1 and O is -2 in most compounds.
 6. The sum of the oxidation numbers in a
compound must equal the charge of the
compound.

Assign oxidation numbers to the
elements in these compounds:
H 2 O
SO4
2-
H 2
BaF2
A redox reaction occurs when the
oxidation number of an element
changes during the reaction.
 2Mg
+ O2  2MgO
 Mg goes from 0 to +2
 O goes from 0 to -2
 O’s oxidation number goes down, or is
reduced. The oxidizer gets reduced.
Assign an oxidation number PER ATOM for each element