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Manganese

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Mn
Mn
Manganum

PERIODIC TABLE OF THE ELEMENTS

MANGANESE

TRANSITION ELEMENT:
MANGANESE GROUP

 

Atomic number:25

Group numbers:7

Period:4

Electronic configuration:[Ar] 3d5 4s2

Formal oxidation number:+2 +3 +4 +7

Electronegativities:1.55

Atomic radius / pm:136.7

Relative atomic mass:54.938045 ± 0.000005

 

Manganese was discovered by Johan Gottlieb Gahn (SE) in 1774. The origin of the name comes from the Latin word magnes meaning magnet, or magnesia nigri meaning black magnesia (MnO2). It is a hard, brittle, grey-white metal with a pinkish tinge. Impure forms are reactive and rust like iron in moist air. Manganese is most abundant ores are pyrolusite (MnO2), psilomelane [(Ba,H2O)2Mn5O10] and rhodochrosite (MnCO3). Pure metal is produced by mixing MnO2 with powered Al and ignited in a furnace. It's used in steel, batteries and ceramics. The steel in railroad tracks can contain as much as 1.2% manganese. It is crucial to the effectiveness of vitamin B1.

PHYSICAL PROPERTIES

Density / g dm-3:7440 (alpha, 293 K)

 6430 (m.p.)

Molar volume / cm3mol-1:7.38 (alpha, 293 K)

 8.54 (m.p.)

Electrical resistivity / μΩcm:144 (20 °C)

THERMAL PROPERTIES

Thermal conductivity / W m-1K-1:7.82

Melting point / °C:1246

Boiling point / °C:2061

Heat of fusion / kJ mol-1:14.4

Heat of vaporization / kJ mol-1:220.5

Heat of atomization / kJ mol-1:279.37

IONIZATION ENERGIES

First ionization energy / kJ mol-1:717.28

Second ionization energy / kJ mol-1:1509.04

Third ionization energy / kJ mol-1:3248.49

ABUNDANCE OF ELEMENTS

in the atmosphere / ppm:-

in the Earth's crust / ppm:1400

in the oceans / ppm:0.002

CRYSTALLOGRAPHIC DATA

body-centered cubic

Crystal structure:

body-centered cubic

Unit-cell dimensions / pm:

a=891.39

Space group:

I43m

ISOTOPES

IsotopeRelative atomic massMass percent (%)
55Mn54.938050(1)100

REDUCTION POTENTIALS

Balanced half-reaction Eo / V
MnIV + e- = MnIII+1.65 (14 mol dm-3 H2SO4)
MnIII + e- = MnII+1.59 (14 mol dm-3 H2SO4)
Mn3+ + e- = Mn2++1.51 (7.5 mol dm-3 H2SO4)
Mn2+ + 2e- = Mn(s)- 1.180
MnO4- + e- = MnO42-+0.564
MnO4- + 2H2O + 3e- = MnO2(s) + 4OH-+0.588
MnO4- + 4H+ + 3e- = MnO2(s) (alpha) + 2H2O+1.695
MnO4- + 4H+ + 3e- = MnO2(s) (beta) + 2H2O+1.679
MnO4- + 8H+ + 4e- = Mn3+ + 4H2O+1.506
MnO4- + 8H+ + 5e- = Mn2+ + 4H2O+1.51
MnO42- + 4H+ + 2e- = MnO2(s) + 2H2O+2.257
MnO42- + 5H+ + 2e- = HMnO2- + 2H2O+1.234
MnO42- + 2H2O + 2e- = MnO2(s) + 4OH-+0.51 (18 °C)
MnO2(s) + 4H+ + e- = Mn3+ + 2H2O+0.948
MnO2(s) (alpha) + 4H+ + 2e- = Mn2+ + 2H2O+1.23
MnO2(s) (beta) + 4H+ + 2e- = Mn2+ + 2H2O+1.22
MnO2(s) (gamma) + 4H+ + 2e- = Mn2+ + 2H2O+0.21
Mn(OH)3(s) + e- = Mn(OH)2(s) + 2OH-+0.1
Mn(CN)63- + e- = Mn(CN)64-- 0.244
Mn(OH)2(s) + 2e- = Mn(s) + 2OH-- 1.55
HMnO2- + 3H+ + 2e- = Mn(s) + 2H2O- 0.163

 

24 Chromium <=
25 Manganese
=> 26 Iron