Unformatted text preview: tance; It is
itself reduced Oxidation
The charge the atom would have in a molecule (or an
ionic compound) if electrons were completely transferred
1. Free elements (uncombined state) have an oxidation number
Na, Be, K, Pb, H2, O2, P4
number : zero
2. In monoatomic ions, the oxidation number is equal to the
Fe = +3
charge on the ion.
Li = +1 Li+ ; Fe3+; O2-,
Fe O = -2 3. The oxidation number of oxygen in compounds is usually –2.
In H2O2 and O22- it is –1.
and 4. The oxidation number of hydrogen is +1 except when it is
bonded to metals in binary compounds, its oxidation number is
–1 in this case.
esp : NaH
5. Group IA metals are +1, IIA metals are +2 and fluorine is
6. The sum of the oxidation numbers of all the atoms in a
molecule or ion is equal to the charge on the molecule or ion
charge on Oxidation numbers of
all the atoms in HCO3- ?
+1 +4 −2 − H CO 3 +1 ? H ClO 2 2− ? Cr O
2 7 +3 −2 H ClO 2 −2 2 − +6 Cr O
2 7 Single Replacement Reactions
All single replacement reactions are redox reactions
The single element is considered “more active” or higher in
the “activity series” than the one in the compound.
more active than
Oxidation half reactions 0 +2 H 2 + CuO oxidizing agent
0 +1 → Cu + H 2O Reduction half reactions The more active an element is, the easier for it to lose electrons
easier Activity Series of Metals in aqueous solution Balancing Redox Equations
Esp: The oxidation of Fe2+ to F...
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