How does iron react with oxygen?
Iron can react with oxygen to form two of its oxides, iron (II, III) oxide and iron (III) oxide.
Upon reacting with oxygen, iron will be oxidized to either the +3 oxidation state in iron (III) oxide, or to a combination of the +2 and +3 oxidation states in iron (II, III) oxide.
The balanced chemical equations for these reactions look like this
#4"Fe"_text((s]) + 3"O"_text(2(g]) -> 2"Fe"""_2"O"_text(3(s])#
#3"Fe"_text((s]) + 2"O"_text(2(g]) -> "Fe"""_3"O"_text(4(s])#
The first compound, iron (III) oxide, also called ferric oxide, is dark red/brown in color
while the second compound, iron (II, III) oxide, also called ferrous ferric oxide, is dark brown/black in color
Here's a video showing the burning of iron in oxygen
SIDE NOTE You will sometimes hear dry Iron (III) oxide powder being referred to as rust, but that is the simplified version of what rust really is, which is a combination of hydrated iron (III) oxide and iron (III) hydroxides.