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Manganese is a brittle, hard metal that is similar to iron. It is required for the manufacture of steel. Manganese can exist in all oxidation states ranging from +2 to +7, but only manganese (II), manganese (IV), and manganese (VII) compounds are stable. Manganese (II) salts dissolve in water and turn a pale pink color. A well-known manganese (iv) compound is brown insoluble manganese (iv) oxide. The plus seven-state is the most common among the transition metals of the fourth period. Manganese (vii) exists in aqueous solution as dark purple manganite (vii) or permanganate ions. Potassium manganite (vii) is a highly reactive oxidant that is used in chemical analysis and synthesis. Surprisingly, the reduction product of manganite (vii) ions is affected by the ph of the solution. Manganite (vii) is reduced to the colorless or pale pink manganese (ii) ion in acidic solution. So, at close to neutral ph values, the reduction product is dark brown manganese (iv) oxide. Let's delve a little deeper into the material now.
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Key Takeaways: Manganese, the periodic table, manganese sulfate, properties, use of manganese.
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What is Manganese?
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Manganese has the chemical symbol Mn and the atomic number 25. It is not found in nature as a free element. It is frequently found in minerals with iron. Manganese is a metal that is widely used in industrial metal alloys, particularly in stainless steel. Historically, manganese is named after pyro Lucite and other black minerals found in Magnesia and Greece, which also gave its name to magnesium in the iron ore magnetide. In the mid-18th century, Swedish-German chemist Carl Wilhelm Scheele used pyrolusite to produce chlorine.
She and others knew Pyrrha Lucite, now known as manganese dioxide, contained a new element, but they couldn't isolate it. In 1774, Johann Godley was the first to isolate an impure sample of manganese metal by reducing the dioxide with carbon-manganese phosphate, which is used to prevent rust and corrosion on steel. Ionized manganese is used in the manufacturing of pigments of various colours, depending on the oxidation state of the ions. Alkali and alkaline earth metal permanganates are strong oxidizers. In zinc-carbon and alkaline batteries, manganese dioxide is used as the cathode electron acceptor material. Manganese ions serve as cofactors for a wide range of enzymes that perform a variety of functions in biology.
Manganese enzymes are especially important in the detoxification of superoxide-free radicals and organisms that must deal with oxygen. Manganese also functions in the oxygen-evolving complex of photosynthetic plants, and the element is a trace mineral required by all known living organisms. It also acts as a neurotoxin, and in higher concentrations, particularly through inhalation, it can cause Manganism, a condition in mammals that causes irreversible neurological damage.
Why is Manganese Interesting?
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Manganese is a much more interesting metal than you might think. It is possible to say element or metal. It is a transition metal, and the transition metal row in the periodic table extends all the way from scandium to zinc. What is it about manganese that makes it so appealing? It is located in the centre of this transition group. Manganese is the fifth of ten transition metals ranging from scandium to zinc. They are ten because each has a specific number of D electrons; one for Scandium, ten for Zinc. So manganese has five atoms in the middle. As a result, it contains exactly half of the D electrons that can be accommodated in the cell.
Manganese has no magnetic properties. But what's the point of being interested in something that isn't magnetic? That's interesting because the first thing you notice about its salts (MnSO4) is that they're almost white. It's just a tad pink. This is surprising because the salt of transition metals is supposed to be colored, but the manganese sulphate here is almost white. Keep in mind that manganese is not magnetic.
However, if you dip the magnet into the manganese sulphate, you will notice that the salt adheres to the magnet. That is extraordinary. Salts are not normally expected to be magnetic, and it is even more surprising if the metal is not magnetic but the salt is. Because it contains five electrons, the salt is magnetic. These five electrons in the D cell are unpaired; they each occupy a different volume of space around the atom.
So each of them has a strong magnetic effect, and all five of them are truly magnetic, and the material's lack of color is also associated with these five electrons. When you drop a colorless solution of manganese sulphate into a solution of sodium hydroxide, you get a precipitate of hydroxide, and because the sodium hydroxide contains oxygen, the oxygen removes one of the electrons from the manganese. As a result, it is now known as manganese 3, which has only four electrons and a nice brown color. As a result, you see this color change. The most well-known manganese compound is potassium permanganate, which is purple in color. Potassium permanganate is denoted as KMnO4. Manganese has no D electrons at all in MnO4 minus the permanganate ion. They've all gone to get some oxygen. You can see a beautiful purple color spreading out if you drop a few tiny crystals of permanganate into water.
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Properties of Manganese
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Manganese is a silvery metal that is hard and brittle. Manganese is far too brittle to be useful as a pure metal. It is primarily found in alloys such as steel. Steel contains about 1% manganese, which increases strength while also improving workability and wear resistance.
Uses of Manganese
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- Manganese is used to make a variety of important alloys, as well as to deoxidize and desulfurize steel.
- It is also used in the manufacture of dry cell batteries.
- Manganese is used in paint as a black-brown pigment.
Read More: Dalton’s atomic theory
Things to Remember
- Manganese is a silvery metal that is hard and brittle. Manganese is far too brittle to be useful as a pure metal. It is primarily found in alloys such as steel.
- Steel contains about 1% manganese, which increases strength while also improving workability and wear resistance.
- Manganese has the chemical symbol Mn and the atomic number 25.
- The most well-known manganese compound is potassium permanganate, which is purple in color. Potassium permanganate is denoted as KMnO4. Manganese has no D electrons at all in MnO4 minus the permanganate ion. They've all gone to get some oxygen.
- Manganese is used to make a variety of important alloys, as well as to deoxidize and desulfurize steel.
- It is also used in the manufacture of dry cell batteries.
- Manganese is used in paint as a black-brown pigment.
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Sample Questions
Ques: What happens when magnesium and oxygen come into contact? (2 marks)
Ans: When magnesium reacts with oxygen, it produces light that is bright enough to temporarily blind you. Magnesium burns so brightly because the reaction produces a great deal of heat. Magnesium gives two electrons to oxygen as a result of this exothermic reaction, resulting in powdery magnesium oxide (MgO). Magnesium oxide is formed as a result of energy liberation.
Ques: Why is Manganese's third ionization energy (Z = 25) so unusually high? (2 marks)
Ans: The atomic number of manganese is 25 and an electronic configuration of [Ar]4s2,3d5 . The loss of two electrons transforms Mn2 + into [Ar]3d5 , a structure with a half-filled d-orbital that is exceedingly stable. As the third electron must be removed from the stable configuration of Mn2 + , the third ionization energy is extremely large.
Ques: Why are Mn2 + compounds more resistant to oxidation to their +3 state than Fe2 + compounds? (2 marks)
Ans: The electronic configuration of Mn2 + is [18Ar]3d5 and the electronic configuration of Fe2 + is [18Ar]3d6. As Mn2 + has a stable half-filled electronic structure, Mn2 + compounds are more resistant to oxidation to their +3 state than Fe2 + compounds. Fe2 + (3d6) can easily lose one electron to become Fe3 + ( 3d5 , stable configuration).
Ques: Name one manganese and one chromium ore each. (1 mark)
Ans: Pyrolusite is the manganese ore, and chromite is the chromium ore.
Ques: Explain why: All bonds formed between manganese and oxygen in permanganate ions are covalent. (2 marks)
Ans: MnO4− in the highest oxidation state, +7. In high oxidation states, transition metals form covalent bonds (according to Fajan's rules, as oxidation state increases, ionic character decreases).
Ques: Write complete chemical equation for: Oxidation of Mn2 + by MnO4− in neutral or faintly alkaline medium. (1 mark)
Ans: 8MnO4 - + 3S2O32 - + H2O→8MnO2 + 6SO42 - + 2OH –
Ques: Complete the equation: MnO2 + KOH + O2→ (1 mark)
Ans: MnO2 + KOH + O2→KMnO4 + H2O
Ques: Determine the number of electrons transferred in each case when KMnO4 is used as an oxidizing agent to give, (3 marks)
(i) MnO2
(ii) Mn2 +
(iii) Mn(OH)3
(iv) MnO42−
Ans: In each case, the number of electrons transferred is:
The oxidation state of manganese in KMnO4 is +7
(i) The oxidation state of manganese in MnO2 is +4. As a result, three electrons will be transferred.
(ii) The oxidation state of manganese in Mn2 + is +2. As a result, five electrons will be transferred.
(iii) The oxidation state of manganese in Mn(OH)3 is +3 . As a result, four electrons will be transferred.
(iv) The oxidation state of manganese inMnO42− is +6. As a result, one electron will be transferred.
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