Manganese Element Properties and Information
Manganese Element Properties and Information
Manganese is the twenty-fifth element on the periodic table. Elements are arranged in the periodic table on the basis of the atomic number. Atomic number is the number of protons in the nucleus of the atom. Manganese has an atomic number of 25. It is located in the Group 7 and Period 4 of the periodic table of elements. It is denoted by Mn. The name is derived from the Latin word ‘Magnes’ which means Magnet.
Johann Heinrich Pott investigated a mineral called pyrolusite in 1740 and found that it did not contain any iron. He was able to make one of the strongest oxidisers using the pyrolusite ore. During 1700s, many chemists tried to separate the unknown metal in pyrolusite. The person who is credited to do this is Johan Gottlieb Gahn. He separated manganese from pyrolusite in 1774. Later it was found that Ignatius Kaim had already separated the manganese metal in 1771 for his dissertation work. The strong oxidiser made by Johann Heinrich Pott is potassium permanganate.
Manganese is the fifth most abundant element on earth. It is not found in free state and is usually present in minerals along with iron. It is a widely distributed element. Its concentration in earth’s crust is about 0.1%. The minerals in which manganese occurs in most quantities are pyrolusite and rhodochrosite. Manganese occurs as manganese dioxide in pyrolusite and as manganese carbonate in rhodochrosite. Manganese nodules have also been found at the bottom of the ocean, the nodules contain about 24% manganese.
Physical Properties
- Manganese is a silvery-grey metal which looks like iron. It is hard and brittle in nature.
- The atomic mass of manganese is 54.938
- The melting point of manganese is 1247°C
- The boiling point of manganese is 2061°C
- The density of manganese is 7430 in S.I. units at 20°C
- Manganese has only one stable isotope which is manganese-55.
Chemical Properties
- Manganese has been observed to form compounds with wide oxidation states. They range from -3 to +7.
- Manganese compounds with +7 oxidation states are extremely powerful oxidisers.
- Manganese(II) compounds are the most stable when compared to all other states.
Methods of Production
- Electrowinning process: In order to produce pure manganese, ores are selected which do not contain iron, the manganese ore leached by sulfuric acid then the manganese diffused to the acid solution is subjected to electrowinning process which removes the manganese from solution and deposits it on the cathode material.
- Heap Leach: The manganese ore is subjected to the natural gas at the bottom of the heap which provides carbon monoxide for reduction of manganese ore to manganese dioxide and also the required temperature of 850°C. The ore is then grinded and put in leach tank where a mixture of sulfuric acid and ferrous ion is used as the leaching solution. The iron reacts with manganese dioxide to form iron hydroxide and elemental manganese.
Relevance in Chemical and Related Industries
- Steel industries: About 85-90% of manganese produced commercially is used in iron and steel industries. Manganese is introduced while steel making in order to remove impurities such as oxygen, sulphur, and phosphorus to improve its malleability. Ferromanganese products often have manganese in the concentrations of 80%.
- Alloys: Aluminium alloys are the second major application of commercially produced manganese. Aluminium having about 1.5% of manganese have high resistance to corrosion and the grain absorbs impurities better.
Relevance in Other Industries
- Engines: A compound of manganese called methylcyclopentadienyl manganese tricarbonyl is used as an additive in unleaded gasoline in order to boost the octane rating and reduce the knocking. The manganese in this compound is present in +1 oxidation state, which is rare.
- Batteries: Manganese(IV) oxide was used as an electron acceptor from zinc in the original dry cell batteries. The manganese dioxide is reduced to manganese oxide-hydroxide during discharging so that the hydrogen does not accumulate at anode. This principle is used in newer alkaline batteries also but with different electrolyte solution.
Health Effects on Exposure
- Shortage: Manganese is an essential element in the human body. If there is any shortage then it leads to blood clotting, skeletal disorders, birth defects, change of hair colour, neurological disorders, etc.
- Poisoning: If too much manganese is present in the body then it becomes toxic and hinders the functioning of the body. When manganese affects brain it causes forgetfulness, hallucinations and nerve damage. When it affects respiratory system it causes lung embolisms and bronchitis.
Effects on Surroundings
- Plants: Manganese is naturally present in soils. If the soil is manganese deficient then it causes disturbance in the plant mechanism. The conversion of water to oxygen and hydrogen requires presence of manganese. It may happen that the manganese content of soil may increase by industrial activities; if too much manganese is absorbed by plants then it causes swelling of cell walls, browning and withering of leaves.
- Animals: If animals consume too little manganese then their growth becomes retarded, the bone formation is hindered and reproductive system also gets affected. Too much manganese can lower the blood pressure, cause lung disturbances, and cause brain damage.
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