Basic Rules

• Any atom in its elemental form (Na, O₂, Mg, Cl₂...) has and oxidation number of zero.
• For monoatomic ions, the oxidation number equals the ion’s charge.
• For polyatomic ions the sum of the constituent atoms’ oxidation numbers is equal to the charge of the ion.
• For neutral compounds the sum of the constituent atoms’ oxidation numbers is equal to zero.

Specific Rules

Element(s)	Oxidation #	Exceptions
Group I	+1	None
Group II	+2	None
F	-1	None
H (with metals and B)	-1	None
H (with non-metals)	+1	None
O	-2	-1 in peroxides or with F
Halogens	-1	with oxygen or halogens higher in column

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