What do the Roman Numerals mean?
The use of Roman numerals in compounds is based on the indication of the oxidation number (as a Roman Numeral) of each of the major elements in the compound, e.g. iron(III) chloride. There is no space between the element name and the oxidation number.

Iron Reaction with Oxygen - Iron Oxide Reaction
Iron oxides are chemical compounds composed of iron and oxygen. There are at least sixteen iron oxides and oxyhydroxides which have a variety of uses ranging from pigments, cosmetics, paints and in construction. When heated, iron reacts with oxygen to form a mixture of iron(II) and iron(III) oxides. The black powder known as wustite, also known as ferrous oxide is Iron(II) oxide (FeO). Iron(II) oxide should not be confused with rust, which usually consists of hydrated iron(III) oxide (ferric oxide). Strong heating is required to make iron powder burn in oxygen. The reaction creates a black solid and produces yellow showery sparks.

Iron + Oxygen —> Iron(II) oxide, Iron(III) oxide

Iron Sulfur Reaction - Iron Sulfide
The exothermic reaction of two elements, iron and sulfur, form the compound, iron sulfide. Iron(II) sulfide or ferrous sulfide is a chemical compound with the formula FeS. Heating the two elements produces an orange glow and iron(II) sulfide is produced. Ferrous sulfate is mainly used as a a reducing agent, mostly for the reduction of chromate in cement. FeS can be obtained by the heating of iron and sulfur:

Fe + S --> FeS

Pyrite is the classic "Fool's Gold" and is used in jewelry under the trade name "marcasite". Powdered iron sulfide will ignite spontaneously in air. Iron reacts with dilute sulphuric acid to form iron sulphate and hydrogen gas.

Iron + Sulphuric acid —> Iron Sulphate + Hydrogen

Iron Hydrochloric Acid reaction
Iron sulfide reacts with hydrochloric acid, releasing the pungent hydrogen sulfide.

FeS + 2 HCl → FeCl2 + H2S

Iron reacts with dilute hydrochloric acid to form iron chloride and hydrogen gas.

Iron + Hydrochloric acid —> Iron Chloride + Hydrogen

Iron and Water Reaction
Iron has virtually has no reaction with cold water.  However, when both water and oxygen are present (moist air), iron corrodes. Its silvery colour changes to a reddish-brown, because hydrated oxides are formed. It does react with steam to give iron oxide and hydrogen gas.

Iron + Steam —> Iron(II) Iron(III) oxide

Chemical Reactions
Some examples of a chemical reaction include most commonly burning, fermentation, tarnishing and rusting. There are several different types of Chemical reaction which have been detailed below:

• Substitution reactions
• Double displacement reactions
• Acid-base reactions
• Combustion reactions
• Combination reactions
• Decomposition reactions