CHM135H1 : Chapter 21.docx
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CHM135H1 Full Course Notes
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Redox reactions and assignment of oxidation numbers, keeping track of electrons in overall stoichiometry of balanced reaction oxidization: losing electrons reduction: gaining electrons. These oxidation numbers are assigned using the following rules: the convention is that the cation is written first in a formula, followed by the anion. For example, in nah, the h is h-; in hcl, the h is h+: the oxidation number of a free element is always 0. The atoms in he and n2, for example, have oxidation numbers of 0: the oxidation number of a monatomic ion equals the charge of the ion. For example, the oxidation number of na+ is +1; the oxidation number of. N3- is -3: the usual oxidation number of hydrogen is +1. The oxidation number of hydrogen is -1 in compounds containing elements that are less electronegative than hydrogen, as in cah2: the oxidation number of oxygen in compounds is usually -2.
