MANGANESE ORE in NTB & NTT
Manganese is a chemical
element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element
in nature (often in combination with iron), and in many minerals. Manganese is
a metal with important industrial metal alloy uses, particularly in stainless
steels.
Historically,
manganese is named for various black minerals (such as pyrolusite)
from the same region of Magnesia in Greece which gave names to
similar-sounding magnesium, Mg, and magnetite,
an ore of the element iron, Fe. By the mid-18th century, Swedish chemist Carl Wilhelm Scheele had used pyrolusite
to produce chlorine.
Scheele and others were aware that pyrolusite (now known to be manganese
dioxide) contained a new element, but they were not able to isolate it. Johan Gottlieb Gahn was the first to
isolate an impure sample of manganese metal in 1774, by reducing the dioxide with carbon.
Manganese phosphating is used as a
treatment for rust and corrosion prevention on steel. Depending on their
oxidation state, manganese ions have various colors and are used industrially
as pigments.
The permanganates
of alkali
and alkaline earth metals are powerful
oxidizers. Manganese dioxide is used as the cathode (electron acceptor)
material in zinc-carbon and alkaline
batteries.
Physical properties
Electrolytically refined manganese chips
and 1 cm3 cube.Manganese is a silvery-gray metal that resembles iron.
It is hard and very brittle, difficult to fuse, but easy to oxidize.[1]
Manganese metal and its common ions are paramagnetic.[2]
Isotopes
Naturally
occurring manganese is composed of one stable isotope,
55Mn. Eighteen radioisotopes have been characterized, with the
most stable being 53Mn with a half-life
of 3.7 million years, 54Mn with a half-life
of 312.3 days, and 52Mn with a half-life of 5.591 days. All of the
remaining radioactive
isotopes have half-lives that are less than three hours and the majority of
these have half-lives that are less than one minute. This element also has
three meta states.[3]
Manganese
is part of the iron
group of elements, which are thought to be synthesized in large stars shortly before the supernova
explosion. 53Mn decays to 53Cr
with a half-life
of 3.7 million years. Because of its relatively short half-life, 53Mn
occurs only in tiny amounts due to the action of cosmic rays
on iron
in rocks.[4]
Manganese isotopic contents are typically combined with chromium
isotopic contents and have found application in isotope
geology and radiometric dating. Mn–Cr isotopic ratios
reinforce the evidence from 26Al
and 107Pd for the early history of the solar system.
Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites
indicate an initial 53Mn/55Mn ratio that suggests Mn–Cr
isotopic composition must result from in
situ decay of 53Mn in differentiated planetary bodies. Hence 53Mn
provides additional evidence for nucleosynthetic
processes immediately before coalescence of the solar system.[3]
The
isotopes of manganese range in atomic weight
from 46 u (46Mn) to 65 u (65Mn).
The primary decay mode
before the most abundant stable isotope, 55Mn, is electron
capture and the primary mode after is beta decay.[3]
Chemical properties
The
most common oxidation states of manganese are +2, +3,
+4, +6 and +7, though oxidation states from −3 to +7 are observed. Mn2+
often competes with Mg2+ in biological systems. Manganese compounds
where manganese is in oxidation state +7, which are restricted to the unstable
oxide Mn2O7 and compounds of the intensely purple
permanganate anion MnO4−, are powerful oxidizing
agents.[1]
Compounds with oxidation states +5 (blue) and +6 (green) are strong oxidizing
agents and are vulnerable to disproportionation.
