Manganese at a glance
- Atomic number
- 25
- Symbol
- Mn
- Atomic mass
- 54.938 u
- Category
- Transition metal
- Group / period
- 7 / 4
- Electron configuration
- [Ar] 3d 5 4s 2
- State at 25 °C
- Solid
- Melting point
- 1246 °C
- Boiling point
- 2061 °C
- Density
- 7.44 g/cm³
- Electronegativity
- 1.55
- 1st ionization energy
- 717 kJ/mol
- Oxidation states
- +2, +4, +7
- Discovered
- 1774
Atomic structure
A neutral manganese atom has 25 protons and 25 electrons, and its most common isotope carries about 30 neutrons. One atom weighs about 9.12 × 10⁻²⁶ kg, so a mole of manganese (6.022 × 10²³ atoms) weighs 54.938 g. That nucleus holds 1.2 neutrons for every proton. The electrons fill 4 shells (K 2, L 8, M 13, N 2), which gives the configuration [Ar] 3d 5 4s 2. As a d-block element, both its outer s electrons and its inner d electrons can take part in bonding, which is why it shows more than one oxidation state. It has only one stable isotope, Mn-55. No other element has a stable isotope with mass number 55, so Mn-55 has no stable isobars; its neighbours on that line decay into it or away from it.
Physical properties
At room temperature (25 °C) manganese is a solid. It melts at 1246 °C and boils at 2061 °C, so it stays liquid across a 815-degree range. It stays solid in a candle flame (about 1000 °C) but would melt in molten iron (1538 °C). Its density is 7.44 g/cm³, 7.44 times as dense as water. Its atoms have a radius of about 140 pm (Chromium next door is 140 pm). In the solid, its atoms pack into a complex cubic lattice.
Chemical behaviour
Its electronegativity is 1.55 on the Pauling scale. Pulling off its outermost electron takes 717 kJ/mol. A bond between manganese and chlorine would be polar covalent, with an electronegativity difference of 1.6. Its common oxidation states are +2, +4, +7, so in compounds you will usually meet it as Mn²⁺, Mn⁴⁺ and Mn⁷⁺. Group 7 also holds Technetium, Rhenium and Bohrium, which share its outer-shell pattern.
Where it comes from
It makes up 950 mg/kg of Earth's crust, the 12th most abundant element there. In the human body it accounts for about 0.00002 % of body mass. It was first identified in 1774, making it the 23rd element to be discovered (counting the 11 known since antiquity together).