Manganese – facts and properties
- Symbol
- Mn
- Atomic number
- 25
- Atomic mass
- 54.938 u
- Period
- 4
- Group
- 7
- Category
- transition metal
- Electron configuration
- [Ar] 3d⁵ 4s²
- Electronegativity
- 1.55
- Atomic radius
- 161 pm
- Valence electrons
- 7
- State at standard conditions
- solid
- Melting point
- 1246 °C
- Boiling point
- 2061 °C
- Density
- 7.3 g/cm³
- Discovered
- 1774
Manganese is a hard, brittle, silvery-grey metal with atomic number 25. Almost every steel contains manganese, and batteries contain it as manganese dioxide. Few elements have as many oxidation states: its compounds range from pale pink manganese(II) salts to deep purple potassium permanganate. Plants need manganese too, because without it photosynthesis could not release oxygen.
Position in the periodic table
Occurrence and extraction
After iron, manganese is the most abundant heavy metal in the Earth's crust; titanium is more common but counts as a light metal because of its low density. It never occurs as a native metal. The main ore is pyrolusite, a blackish-brown manganese dioxide. Large deposits are found in South Africa, Gabon and Australia. The deep-sea floor also holds huge numbers of manganese nodules, potato-sized lumps of manganese and iron oxides that also contain nickel, copper and cobalt. Whether and how they may be mined is disputed because of the effects on deep-sea life.
Manganese dioxide has been used since the Stone Age: black pigment made from manganese oxides appears in cave paintings, and glassmakers used it to remove the greenish tint from glass. In 1774 the Swedish chemist Carl Wilhelm Scheele recognised that it contained an unknown element. In the same year his friend Johan Gottlieb Gahn isolated the metal by strongly heating the dioxide with carbon. The name goes back to the ancient region of Magnesia, which also gave magnesium its name, and the similar names caused confusion for a long time.
Today manganese ore is reduced in electric furnaces together with iron ore to make ferromanganese, which goes straight into steelmaking. Pure manganese is obtained by electrolysis of manganese sulfate solutions.
Properties and reactions
Manganese is in period 4 and group 7, and its electron configuration is [Ar] 3d⁵ 4s². Its electronegativity is 1.55. The metal has a density of 7.3 g/cm³, melts at 1246 °C and boils at 2061 °C. It is very hard and so brittle that the pure metal is hardly used on its own. Manganese is more reactive than iron: it tarnishes in moist air and dissolves in dilute acids, releasing hydrogen.
Manganese can give up as many as seven electrons and has many oxidation states. The most stable is manganese(II), whose salts are almost colourless to pale pink in solution. Manganese(IV) is found in brownish-black manganese dioxide, MnO₂. The highest state, plus seven, occurs in the permanganate ion, MnO₄⁻. Potassium permanganate forms dark purple crystals that dissolve to give an intensely purple solution. It is a strong oxidising agent. In school labs it is used for redox titrations: as long as the sample still contains something to oxidise, permanganate is reduced to almost colourless manganese(II) and its colour disappears. Once a faint pink colour stays, the end point has been reached, so no separate indicator is needed.
Uses in everyday life and technology
Around nine tenths of all manganese mined goes into the steel industry. In molten steel, manganese binds sulfur and oxygen, which makes the steel easier to shape. It also increases strength and hardness. Manganese steel with a high manganese content becomes harder at the surface the more it is hammered, so it is used for railway points, digger teeth and rock crushers. Aluminium is alloyed with manganese as well, for example for drinks cans.
Manganese dioxide is part of the cathode in alkaline and zinc–carbon batteries, so it is inside most ordinary disposable batteries. In many lithium-ion batteries for electric cars, the cathode material contains manganese alongside lithium, nickel and cobalt. Potassium permanganate is used in water treatment and as a disinfectant.
For living things, manganese is an essential trace element that activates many enzymes. At the heart of photosynthesis in plants sits a cluster of manganese, calcium and oxygen that splits water and releases oxygen. People get enough manganese from wholegrain foods, nuts and tea. Breathing in large amounts of manganese dust over many years, for example when welding without protection, can damage the nervous system.
Molecules containing this element
- Manganese(II) oxide MnO
- Manganese(II) carbonate MnCO3
- Manganese(II) sulfate MnSO4
Quick question
What is the atomic number of manganese (Mn)?
FAQ
What is the difference between manganese and magnesium?
They are two completely different elements. Magnesium is a light alkaline earth metal in group two, while manganese is a heavy, hard transition metal. Both names go back to the ancient region of Magnesia, where minerals of both elements were found, which is why they were often confused in the past.
What is manganese used for?
Mainly for steel, where manganese binds sulfur and oxygen in the melt and makes the steel stronger. It is also found as manganese dioxide in disposable batteries, in many lithium-ion batteries and in aluminium alloys. Potassium permanganate is used as an oxidising agent and disinfectant.
Is manganese good for you?
In small amounts, yes. Manganese is a trace element that many enzymes need, and it is found in wholegrain bread, nuts, pulses and tea. Deficiency is rare. Manganese becomes harmful when large amounts of manganese dust or welding fumes are inhaled over a long period.