02/05/2026
The Claymont Science Club was back in action today after a weather-induced hiatus!
Our members were able to create a series of colorful solutions containing manganese ions (albeit some were short-lived) and solids to show the various hues produced by the six oxidation states of element 25, manganese.
An oxidation state (or oxidation number) in chemistry is a hypothetical charge an atom would have if all its bonds were 100% ionic, indicating the number of electrons lost (positive state), gained (negative state), or shared in a compound, crucial for tracking electron changes in redox reactions. It's a formalism, not necessarily the atom's real charge, used to understand electron transfer, with rules assigning these numbers, like elements in their pure form having a state of zero, and the sum in a neutral compound being zero.
While manganese has six oxidation states, it does not exist as an ion having a +5, +6, or +7 charge. These three oxidation states of manganese are found in the polyatomic ions of MnO4^3-, MnO4^21, and MnO4^- respectively. These manganese atoms in these structures lose or gain electrons when the ions are oxidized or reduced.
The +2 oxidation state is the most stable form of manganese, meaning it is in its lowest energy, most thermodynamically favored state, typically achieving a full outer electron shell (octet rule) or a stable partially filled d-orbital configuration. This state minimizes energy, reducing reactivity, and is often found in nature or produced readily in compounds.
Common manganese (II) compounds include manganese sulfate and manganese chloride. In aqueous solution, the manganese (II) ion exists as the Mn(H2O)6^2+ complex ion and has an octahedral geometry. Such compounds are usually pale pink in color. The paleness is a consequence of the d^5 electron configuration. Each orbital has a single electron and any electron transitions are spin-forbidden. In nonaqueous solvents the manganese (II) ion forms numerous complexes that have a tetrahedral geometry. These tend to be much more intensely colored than the pale-pink octahedral ions. They are yellow-green in color, and sometimes exhibit fluorescence, which means visible or invisible radiation may be emitted by certain substances as a result of incident radiation of a shorter wavelength such as X-rays or ultraviolet light.
In nature, manganese usually occurs as an oxide (bonded with oxygen). The primary industrial use of manganese is in the manufacturing of steel. The addition of manganese to steel increases its toughness and durability. Manganese is also used to make alloys such as manganese bronze, which is an alloy of copper, zinc, and manganese. This alloy is used for heavy-duty, wear resistant applications. It is commonly used for marine propellers, bushings, bearings, gears, valve stems, and industrial, automotive, and aerospace hardware requiring high strength and durability, especially in saltwater environments. In elemental form, manganese is fairly reactive and will displace hydrogen from acids. Manganese exists in a wide range of oxidation states, including +7, +6, +5, +4, +3, and +2.
The highest oxidation state of manganese is the +7 state, corresponding to the complete removal of all the electrons from the 4s and 3d orbitals. A very good example of a compound in this oxidation state is the permanganate ion, MnO4^-. As a solid, crystals of potassium permanganate are so intensely colored they appear black. Solutions containing the permanganate ion are also intensely colored (purple). The permanganate ion is a strong oxidizing agent (it readily accepts electrons from other substances) and is commonly used in the chemistry laboratory for this purpose. A common oxidation-reduction titration involves the addition of a potassium permanganate solution to a solution containing the oxalate ion or the iron (II) ion. Manganese also exists in the +6 state in the form of manganate ion, MnO4^2- which is a green color in solution created from the reduction (gain of electrons) of the permanganate ion. It is only stable in basic solution. The +4 oxidation state of manganese is found in manganese dioxide, MnO2, which is a stable dark brown or black solid.
