**Look for any H's, O's, or F's in the equation **

**1) Any element just by itself not in a compound, their oxidation number is 0 **

**ex: H2's oxidation number is 0 **

**2) The oxidation number of H is always +1, unless its just by itself (see #1) **

**3) The oxidation number of O is always -2, unless its just by itself (see #1) **

**4) The oxidation number of F is always -1, unless its just by itself (see#1) **

**5) The sum of oxidation numbers in a compound add up to 0 (when multiplied by the subscripts!!!) (see above example) **

**6) The sum of oxidation numbers for a compound is the charge (for example, PO4 has a charge of (-3) SOO... **

**...oxidation no. of O = -2. (there are 4 O's = -8 charge on that side ) P must have an oxidation number of 5. (-8+5= -3), and -3 is the total charge of the compound. **

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