Manganese (Mn)

Manganese is the fourth most-used metal by tonnage after iron, aluminium and copper, and almost all of it disappears invisibly into steel — steelmaking simply does not work without it. Hadfield steel, about 12% manganese, has the unusual property of getting harder the more it is battered, which is why it lines rock crushers and railway crossings. Manganese sits at the heart of the oxygen-evolving complex in photosynthesis: a cluster of four manganese atoms in every plant is what splits water and releases the oxygen in the air.

Properties

Atomic number

25

Symbol

Mn

Standard atomic weight

54.938 u

Category

Transition metal

Group

7

Period

4

Block

d-block

Electron configuration

[Ar] 4s² 3d⁵

Electrons per shell

2, 8, 13, 2

Melting point

1,519 K — 1245.8 °C — 2274.5 °F

Boiling point

2,334 K — 2060.8 °C — 3741.5 °F

Density

7.3 g/cm³

Electronegativity

1.55 (Pauling)

Oxidation states

+7, +4, +3, +2

Discovered

1774 by Johan Gottlieb Gahn

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵

Noble gas shorthand

[Ar] 4s² 3d⁵

Shells

K: 2 · L: 8 · M: 13 · N: 2

What it is used for

• Steelmaking — it removes sulfur and oxygen, and nearly all steel contains some
• Manganese dioxide as the cathode in alkaline and zinc-carbon batteries
• Hadfield steel for rock crushers, railway points and excavator teeth
• Potassium permanganate as a disinfectant and water treatment oxidant
• Decolourising glass, which is why it was once called glassmakers' soap

Hazards

• Chronic inhalation of manganese fume causes manganism, a permanent Parkinson-like condition
• Welders and miners are the usual exposure groups

Neighbours in the table

Group 7

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Manganese sits in group 7 with technetium, rhenium, bohrium.