Atomic number 25

Manganese

Mn
+ phase
− phase

Shells Orbitals 3d 4s

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25 electrons in 4 shells: 2, 8, 13, 2.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Transition metal
Period: 4
Group: 7
Block: d
Standard atomic weight: 54.938(1) Da
Electron configuration: [Ar] 3d⁵ 4s²
Phase at 25 °C: solid
Melting point: 1246 °C
Boiling point: 2061 °C
Density: 7.3 g/cm³
Electronegativity (Pauling): 1.55
Discovered: 1774, Johan Gottlieb Gahn; proposed as an element by Carl Wilhelm Scheele the same year

Neighbours in the table

Cr Fe

Manganese sits at the midpoint of the first transition series, and its 25 electrons show why. Their configuration, [Ar] 3d⁵ 4s², means an argon core, a 4s pair and five 3d electrons, or 2, 8, 13 and 2 across four shells. Hund’s rule, which keeps electrons unpaired where orbitals share an energy, puts one in each 3d orbital. OpenStax counts 4s and 3d electrons alike as a transition metal’s valence electrons, so manganese has seven.

All seven count as removable, on the bookkeeping that treats every bond as ionic. For scandium through manganese, OpenStax says, the top oxidation state means losing every s and d valence electron. Past manganese that stops being possible. The count of common states peaks mid-series and then falls. Los Alamos lists states from −3 to +7; when two go, the 4s pair leaves first and Mn²⁺ keeps all five in 3d.

Bonding follows the state: low states give ionic compounds and basic oxides, high ones covalent compounds and acidic oxides. Manganese(VII) oxide gives HMnO₄ in water; its anion, permanganate, is reduced to Mn²⁺ at +1.51 V. The metal is grey-white like iron but, Los Alamos says, harder and very brittle. Of its four allotropes, gamma is reported soft and easily cut, reverting to alpha at ordinary temperatures.

Where it is found

PubChem’s element record gives 9.50 × 10² milligrams of manganese per kilogram of crust and 2 × 10⁻⁴ milligrams per litre of seawater. ATSDR’s note on the safety record says the pure metal does not occur in nature; it comes combined with elements such as oxygen, sulfur or chlorine. Los Alamos names oxides, silicates and carbonates as the commonest minerals, pyrolusite, MnO₂, and rhodochrosite, a carbonate, among them.

Natural manganese is a single stable isotope, manganese-55. A radioactive one, manganese-53, forms where cosmic-ray protons strike iron in rocks and builds up with a half-life of 3.7 million years. IUPAC’s isotope notes on PubChem’s record describe reading that accumulation as a landform’s exposure age and erosion rate.

Los Alamos reports ocean-floor nodules, about 24 per cent manganese, that may become a source. The US Geological Survey estimates 20 million metric tons of contained manganese mined in 2024, South Africa 7.4 million and Gabon 4.6 million. South Africa also holds about 70 per cent of the world’s resources. The United States mined none, has produced no ore of 20 per cent manganese or richer since 1970, and imports all it uses.

Why it matters

Nearly 90 per cent of each year’s manganese goes into steel, on Jefferson Lab’s figure. Added to the molten metal it removes oxygen and sulfur. Left in the alloy it makes the steel easier to form and work, and raises its strength and resistance to impact. Jefferson Lab notes that railway track carries up to 1.2 per cent manganese. The US Geological Survey finds no satisfactory substitute for it in its major uses and lists it among US critical minerals.

In a zinc-carbon dry cell the paste packed around the graphite rod holds manganese(IV) oxide with zinc chloride, ammonium chloride and water. At that rod the oxide takes up electrons and becomes Mn₂O₃ while the zinc can is oxidised, and the cell gives about 1.5 V. Jefferson Lab describes the oxide’s job as stopping hydrogen from forming. An alkaline cell runs the same manganese reduction, gives +1.43 V, and delivers three to five times as much energy as a zinc-carbon cell the same size.

Glassmakers use the dioxide to cancel the green that iron impurities give glass, and manganese on its own tints glass amethyst. Los Alamos and Jefferson Lab both credit it with the colour of the natural gemstone. Permanganate, a powerful oxidiser, serves in quantitative analysis and in medicine.

Properties

Properties of manganese Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	25
Standard atomic weight	54.938(1) Da	Da	IUPAC/CIAAW 2024
Melting point	1246 °C	°C	Los Alamos: 1246 °C
Boiling point	2061 °C	°C	Los Alamos: 2061 °C
Density	7.3 g/cm³	g/cm³
Electronegativity (Pauling)	1.55
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
Phase at 25 °C	solid

Safety

A steel rail or a battery is not what PubChem’s record describes: for the elemental metal, 46.1% of European reports find no GHS hazard. Others flag a flammable solid, the finely divided dust, and eye irritation. Japan and Australia add Danger for repeated-exposure organ damage; Japan names the nervous system and lungs, and adds fertility. The nervous damage is manganism, weakness, tremors and a mask-like face after long-term inhalation in ferroalloy foundries, dry-battery plants, welding and mines. Dietary manganese is a nutrient; the PubChem Laboratory Chemical Safety Summary and NIOSH pocket guide below cover workplaces.

Questions

Who discovered manganese?

Two Swedish chemists, in 1774. Carl Wilhelm Scheele proposed it as an element, and Johan Gottlieb Gahn isolated the metal later that year by heating pyrolusite, MnO₂, with charcoal, on Jefferson Lab's account. Los Alamos credits Torbern Olof Bergman and others with recognising the element, and Gahn with isolating it by reducing the dioxide with carbon.

Is manganese magnetic?

Not as the plain metal. Los Alamos says manganese metal is ferromagnetic, magnetic in the way iron is, only after special treatment. Its alloys are another matter: Los Alamos calls those with aluminium and antimony, and above all with a little copper, highly ferromagnetic. The name itself records magnetism: CIAAW and Los Alamos both trace it to the Latin magnes, magnet, because pyrolusite, its dioxide ore, has magnetic properties.

How is manganese extracted from its ore?

Gahn's method of 1774, reducing the dioxide with carbon, still shows the principle. OpenStax says carbon is a strong enough reducing agent for most d-block metals, whose free elements are not hard to reach. Jefferson Lab gives the modern routes from pyrolusite: burning it in a furnace with powdered aluminium, or treating it with sulfuric acid to make manganese sulfate and electrolysing that. Los Alamos adds sodium and magnesium as reducing metals.

What does manganese do in the body?

It is a trace mineral that comes from the diet. OpenStax's nutrition table lists nuts, seeds, whole grains and legumes as its sources. Its functions there are the formation of connective tissue and bone, blood clotting, sex hormone development, metabolism, and brain and nerve function; deficiency shows as infertility, bone malformation, weakness and seizures. ATSDR's note on PubChem's safety record calls it necessary for good health.

Compounds containing manganese

KMnO₄ Potassium permanganate 6 atoms in one formula unit of an ionic lattice.