Page 361 - Chemistry eBook
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Oxidation Number Rules
1. FREE ELEMENTS (elements that aren’t combined with other elements) have an oxidation state of zero.
Na, Zn, O2, Cl2 all have an oxidation state of zero. Their oxidation state will be written like this: Na0, Zn0, O20, Cl20
2. Within each compound, the sum of all the oxidation numbers must equal zero.
In order to know if the reaction was reduction, oxidation,
or redox, we must know the following special rules that tell us the oxidation states of compounds and elements.
NaCl. Na’s oxidation state is +1 (see Periodic Table).
Cl’s oxidation state is -1 (see Periodic Table). +1 – 1 = 0
There are many Regents questions based on the oxidation number rules.
Free items cost zero. Free elements have an oxidation state of zero.
UNIT 10: OXIDATION & REDUCTION © 360
