Iron(II), or Fe2+ ions and iron(III), or Fe3+ ions, primarily differ in their number of electrons, where iron(II) ions contain one more electron than iron(III) ions. The shorthand electron configurations of iron(II) and iron(III) are [Ar]3d6 and [Ar]3d5, respectively.
Iron is represented in the periodic table with the symbol Fe and atomic number 26. It is the fourth most predominant element found on the surface of the Earth. Iron is a silvery-white or grayish metal that is characterized by its high solubility in acids and tendency to easily react with oxygen to form iron oxide, commonly known as rust.
Iron commonly exists in two primary oxidation states: +2 and +3. When iron loses two electrons, it gains a +2 oxidation state and becomes the iron(II) ion, also known as ferrous ion. When iron loses three electrons, it gains a +3 oxidation state and becomes the iron (III) ion, also referred to as ferric ion.
Ferrous and ferric ions produce different colors in solutions. Ferrous ions are typically pale green in color, but turns violet when dissolved in water. When ferrous ions bond with amine ligands, a red-orange compound ion is formed. Most ferric ion solutions appear yellow or yellow-brown. A combination of ferric ions with thiocyanate ions produces a blood-red substance.
In terms of magnetism, a ferrous ion that normally has paramagnetic properties can become diamagnetic due to the formation of low-spin complexes. A ferric ion, meanwhile, is only paramagnetic as a direct result of its one lone electron.