Ferrous oxide is more correctly called iron(II) oxide.

In chemistry, the adjective ferrous indicates a compound that contains iron(II), meaning iron in its +2 oxidation state, possibly as the divalent cation Fe²⁺. It is opposed to ferric, or iron(III), meaning iron in its +3 oxidation state, such as the trivalent cation Fe³⁺.^[1] This usage has been largely replaced by the IUPAC nomenclature, which calls for the oxidation state being indicated by Roman numerals in parentheses, such as iron(II) oxide for ferrous oxide (FeO), iron(III) oxide for ferric oxide (Fe₂O₃), and iron(II,III) oxide for the oxide Fe₃O₄ that contains both forms of iron.

Pourbaix diagram of aqueous iron

Outside chemistry, ferrous means generally "containing iron".^[1] The word is derived from the Latin word ferrum ('iron').^[2] Ferrous metals include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel).^[3] Non-ferrous is used to describe metals and alloys that do not contain an appreciable amount of iron.^[4]

The term ferrous is usually applied only to metals and alloys. The adjective ferruginous is used instead to refer to non-metallic substances that contain iron, such as ferruginous water; or to an orangish-brown color resembling that of rust.^[5]

Gallery

See also

• Ferric – The element iron in its +3 oxidation statePages displaying short descriptions of redirect targets — [ Iron(III)] compounds
• Ferromagnetism – Mechanism by which materials form into and are attracted to magnets
• Ferrous metal recycling – Recyclable materials left over from manufactured products after their usePages displaying short descriptions of redirect targets
• Iron(II) oxide – Inorganic compound with the formula FeO (ferrous oxide)
• Iron(II) bromide – chemical compoundPages displaying wikidata descriptions as a fallback (ferrous bromide)
• Steelmaking – Process for producing steel from iron ore and scrap

References

Look up ferrous or nonferrous in Wiktionary, the free dictionary.