Element Name: Iron
Element symbol: Fe
Atomic weight of element: 55.85
Element type: metal element
Number of protons: 26
Neutron number: 30
Atomic number: 26
Period: 3
Number of families: eight
Electron shell distribution: 2-8- 14-2
Name origin: Anglo-Saxon: iron (iron); The element symbol comes from the Latin word "iron".
Element Description: Flexible and malleable silvery white metal. It ranks fourth in the earth's crust (56,300 parts per million) and ninth in the universe.
Element source: from iron ore. Limestone, coke and iron ore are put into the blast furnace in layers, and high-temperature airflow is blown from the bottom to make the coke turn hot and red, so iron is reduced from the oxide, melted into liquid state and flows out from the bottom.
Distributed iron is one of the most widely distributed metals on the earth. It occupies about 5. 1% of the earth's crust, ranking fourth in the element distribution sequence, second only to oxygen, silicon and aluminum.
Properties Iron is a shiny silvery white metal, hard and malleable, with melting point 1535 and boiling point of 3000. It has strong ferromagnetism, good plasticity and thermal conductivity.
abstract
Iron is a chemical element and the most commonly used metal. It is a transition metal.
Iron is a lively and strong reducing agent with valence of 0, +2, +3 and +6, and the most important valence states are +2 and +3. At room temperature, iron can slowly replace hydrogen from water, and the reaction speed is accelerated above 500℃:
Iron is difficult to react with oxygen in dry air, but it is easy to corrode in humid air, and it corrodes faster if it is in acid gas or halogen vapor atmosphere. Iron can reduce gold, platinum, silver, mercury, copper or tin plasma from solution.
Formation of iron
The relative atomic mass is 55.847. Iron has many allotropes. Iron is a relatively active metal, which ranks ahead of hydrogen in the metal activity sequence table. At normal temperature, iron is not easy to react with nonmetallic elements such as oxygen, sulfur and chlorine in dry air, but it reacts violently at high temperature. Iron burns in oxygen to generate Fe3O4, and red-hot iron reacts with water vapor to generate Fe3O4. Iron is easily dissolved in dilute inorganic acid and concentrated hydrochloric acid to form divalent iron salt and release hydrogen. When it meets concentrated sulfuric acid or concentrated nitric acid at room temperature, an oxide protective film is formed on the surface to "passivate" iron, so iron products can be used to contain concentrated sulfuric acid or concentrated nitric acid. Iron is a valence-changing element, and its common valence states are +2 and +3. When iron reacts with sulfur, copper sulfate solution, hydrochloric acid and dilute sulfuric acid, it loses two electrons and becomes +2 valence. It reacts with Cl2, Br2, nitric acid and hot concentrated sulfuric acid and is oxidized to Fe3+. Fe3O4 produced by the reaction of iron with oxygen or water vapor can be regarded as FeO Fe2O3, in which 1/3 of Fe is +2 and the other 2/3 is +3. The trivalent compounds of iron are relatively stable. This is a bright silvery white metal. The density is 7.86 g/cm3. Melting point 1535℃, boiling point 2750℃. The common valence is +2 and +3, which has good ductility and thermal conductivity. Can also conduct electricity. Pure iron can be magnetized and demagnetized quickly. The ionization energy is 7.870 electron volts. Because of its active chemical properties, it is a good reducing agent. If there are impurities, it is easy to rust in humid air; In humid air containing acid gas or halogen vapor, rust will be faster. Soluble in dilute acid. Can be passivated in concentrated nitric acid. It can be combined with halogen, sulfur, silicon, carbon and phosphorus when heated. In addition to +2 and +3 valence oxides, there is also a composite oxide Fe3O4 (which is a magnetic oxide). Iron is an indispensable metal in the industrial sector.
Chemical properties of iron
[One of the chemical properties of iron]
Iron Fe, atomic number 26, relative atomic mass 55.847. There are many allotropes of iron, such as iron, iron and iron. Iron is a relatively active metal, which ranks ahead of hydrogen in the metal activity sequence table. At normal temperature, iron is not easy to react with nonmetallic elements such as oxygen, sulfur and chlorine in dry air, but it reacts violently at high temperature. Iron burns in oxygen to generate Fe3O4, and red-hot iron reacts with water vapor to generate Fe3O4. Iron is easily dissolved in dilute inorganic acid and concentrated hydrochloric acid to form divalent iron salt and release hydrogen. When it meets concentrated sulfuric acid or concentrated nitric acid at room temperature, an oxide protective film is formed on the surface to "passivate" iron, so iron products can be used to contain concentrated sulfuric acid or concentrated nitric acid. Iron is a valence-changing element, and its common valence states are +2 and +3. When iron reacts with sulfur, copper sulfate solution, hydrochloric acid and dilute sulfuric acid, it loses two electrons and becomes +2 valence. It reacts with Cl2, Br2, nitric acid and hot concentrated sulfuric acid and is oxidized to Fe3+. Fe3O4 produced by the reaction of iron with oxygen or water vapor can be regarded as FeO Fe2O3, in which 1/3 of Fe is +2 and the other 2/3 is +3. The trivalent compounds of iron are relatively stable.
[The second chemical property of iron]
The electronic configuration of iron is (Ar)3d64s2, and its oxidation states are 0, +2, +3, +4, +5 and +6. Iron is a strong reducing agent with active chemical properties, which can slowly replace hydrogen in water at room temperature, and the reaction rate increases above 500℃.
3Fe+4H2O→Fe3O4+4H2
It is difficult for iron to react with oxygen in dry air, but it is easy to corrode in humid air, and the corrosion is faster if it contains acid gas or halogen vapor. Iron can reduce gold, platinum, silver, mercury, bismuth, tin, nickel or copper plasma from solution, for example:
Copper sulfate+iron → ferrous sulfate+copper
Iron is dissolved in non-oxidizing acids such as hydrochloric acid and dilute sulfuric acid to form ferrous ions and release hydrogen; In cold dilute nitric acid, ferrous ions and ammonium nitrate are formed;
Iron+sulfuric acid → ferrous sulfate+H2 =
4Fe+ 10 HNO 3→4Fe(NO3)2+nh4no 3+3H2O
Iron is dissolved in hot or concentrated nitric acid to produce iron nitrate and release nitrogen oxides. In concentrated nitric acid or cold concentrated sulfuric acid, the surface of iron will form an oxide film and be passivated. Iron reacts violently with chlorine when heated. Iron can also be directly combined with sulfur, phosphorus, silicon and carbon. Iron and nitrogen can not be directly combined, but react with ammonia to form iron nitride Fe2N.
The most important oxidation states of iron are +2 and +3. Ferrous ion is light green, and it is easy to be oxidized into trivalent iron ion in alkaline solution. With the increase of hydrolysis degree, the color of iron ions changed from orange to brown. Both divalent and trivalent iron are easy to form stable coordination compounds with inorganic or organic ligands, such as
Phen is o-phenanthroline, and the coordination number is usually 6. Zero-valent iron can also form various carbonyl irons with carbon monoxide, such as Fe(CO)5, Fe2(CO)9, Fe3(CO) 12, etc. Iron carbonyl is volatile, and its vapor is highly toxic. Iron also has +4, +5 and +6 valence compounds, but only +6 valence compounds in aqueous solution.
There are two main types of compounds: ferrous (II) and ferric (III) compounds. Ferrous compounds include ferrous oxide, ferrous chloride, ferrous sulfate and ferrous hydroxide. Iron-containing compounds include iron oxide, ferric chloride, ferric sulfate and ferric hydroxide.
For example, in potassium ferrocyanide K4 [Fe (CN) 6] 3H2O and potassium ferricyanide K3[Fe(CN)6]. Ferrocene is a compound of iron and cyclopentadiene, and it is a metal-organic compound with sandwich structure.
Three States of Chemical Properties of Iron
The electronic configuration of iron is (Ar)3d64s2, and its oxidation states are 0, +2, +3, +4, +5 and +6. Iron is a strong reducing agent with active chemical properties. Hydrogen in water can be slowly replaced at room temperature, and the reaction rate increases above 500℃: 3Fe+4H2O→Fe3O4+4H2.
It is difficult for iron to react with oxygen in dry air, but it is easy to corrode in humid air, and the corrosion is faster if it contains acid gas or halogen vapor. Iron can reduce gold, platinum, silver, mercury, bismuth, tin, nickel or copper plasma from solution, such as CuSO4+Fe→FeSO4+Cu.
Iron is dissolved in non-oxidizing acids such as hydrochloric acid and dilute sulfuric acid to form ferrous ions and release hydrogen; In cold dilute nitric acid, ferrous ions and ammonium nitrate are formed;
Fe+h2so 4→feso 4+H2↑4Fe+ 10 HNO 3→4Fe(NO3)2+nh4no 3+3H2O
Formation of iron nitride Fe2N
Iron is dissolved in hot or concentrated nitric acid to produce iron nitrate and release nitrogen oxides. In concentrated nitric acid or cold concentrated sulfuric acid, the surface of iron will form an oxide film and be passivated. Iron reacts violently with chlorine when heated. Iron can also be directly combined with sulfur, phosphorus, silicon and carbon. Iron and nitrogen can not be directly combined, but react with ammonia to form iron nitride Fe2N.
The most important oxidation states of iron are +2 and +3. Ferrous ion is light green, and it is easy to be oxidized into trivalent iron ion in alkaline solution. With the increase of hydrolysis degree, the color of iron ions changed from orange to brown. Both divalent and trivalent iron are easy to form stable coordination compounds with inorganic or organic ligands, such as
Phen is o-phenanthroline, and the coordination number is usually 6. Zero-valent iron can also form various carbonyl irons with carbon monoxide, such as Fe(CO)5, Fe2(CO)9, Fe3(CO) 12, etc. Iron carbonyl is volatile, and its vapor is highly toxic. Iron also has +4, +5 and +6 valence compounds, but only +6 valence compounds in aqueous solution.
There are two main types of compounds: ferrous (II) and ferric (III) compounds. Ferrous compounds include ferrous oxide, ferrous chloride, ferrous sulfate and ferrous hydroxide. Iron-containing compounds include iron oxide, ferric chloride, ferric sulfate and ferric hydroxide.
For example, in potassium ferrocyanide K4 [Fe (CN) 6] 3H2O and potassium ferricyanide K3[Fe(CN)6]. Ferrocene is a compound of iron and cyclopentadiene, and it is a metal-organic compound with sandwich structure.
Element source
Iron is an abundant element in the earth's crust, second only to oxygen, silicon and aluminum. Magnetite, hematite, limonite and siderite are important iron ores. Monomer metals are usually made of coke, iron ore and Carboniferous stones. Pure iron can be obtained by reducing pure iron oxide with hydrogen. Iron with carbon content exceeding 1.7% is called pig iron (or cast iron). Iron melt with carbon content less than 0.2% is called wrought iron or wrought iron. Iron melt with carbon content between 1.7-0.2 is called steel. Pig iron is hard, but brittle; Steel is elastic; Wrought iron is easy to process, but softer than steel. Pig iron steelmaking is to reduce the carbon content in pig iron and remove impurities such as silicon, sulfur and phosphorus.
Element usage
Its biggest use is steelmaking; It is also widely used to make cast iron and wrought iron. Iron and its compounds are also used as magnets, dyes (ink, blue printed cloth, rouge pigment) and abrasives (red iron powder). Reduced iron powder is widely used in metallurgy.
Element auxiliary data
One of the main components of the crust. Iron is widely distributed in nature, but it was discovered and utilized later than gold and copper. First of all, there is no iron in the state of natural elements on the earth, which is easy to oxidize and rust. In addition, its melting point (1535℃) is much higher than that of copper (1083℃), and it is more difficult to smelt than copper.
Humans first discovered that iron is a meteorite falling from the sky, and the percentage of iron in meteorites is very high (90.85% in iron meteorites), which is a mixture of iron, nickel and cobalt. Archaeologists once found an axe made of meteorites in the ancient tomb; In the religious scriptures hidden in the pyramids of the fifth and sixth dynasties in Egypt, it was recorded that the thrones of important gods such as the sun god were made of iron at that time. Iron was considered as the most mysterious precious metal at that time, and the Egyptians simply called it "Shi Tian". In ancient Greek, "star" and "iron" are the same word.
1978, a Shang Dynasty tomb was excavated in Liuhe Village, Pinggu County, Beijing, and many bronzes were unearthed. The most striking thing is an ancient iron-edged bronze cymbal, which was identified as forged by meteorites. This not only shows that the earliest iron discovered by human beings came from meteorites, but also shows that the working people in our country knew iron and were familiar with its forging properties more than 3300 years ago, and realized the difference in nature between iron and bronze.
Because the source of meteorites is extremely scarce, the iron obtained from meteorites has little effect on production. With the maturity of bronze smelting technology, it has gradually created conditions for the development of iron smelting technology. The earliest artificial iron smelting in China appeared at the turn of the Spring and Autumn Period and the Warring States Period, about 2500 years ago. China's steelmaking technology also developed very early. 1978, the cultural relics excavation team of Changsha Railway Station Construction Project of Hunan Provincial Museum unearthed a steel sword from an ancient tomb, and the shape, decoration and shape of the pottery buried in the ancient tomb were identified as the tombs in the late Spring and Autumn Period. The steel used in this sword is medium carbon steel with a carbon content of about 0.5%, and the metallographic structure is relatively uniform, which indicates that it may be overheated.
The ironmaking skills of the ancient working people were also outstanding. The iron pillar erected behind the gate of a mosque near Delhi, India, is made of rather dull iron. How to produce such iron at that time was considered a miracle by modern people. According to human analysis, the iron content is more than 99.72%, and the rest is carbon 0.08%, silicon 0.046%, sulfur 0.006% and phosphorus 0. 1 14%.
A foundry worker named Bessemer initiated a new era of modern steelmaking. He announced his tiltable converter on August 1856+0 1.
With the development of industry, a lot of scrap steel and scrap iron appeared in production, construction and life, which could not be used in converter, so open hearth steelmaking appeared, which was founded by Siemens brothers in Germany and Martin brothers in France at the same time, and the time was 65438+early 1960s.
Iron is also one of the essential elements for human body. There are about 4-5 grams of iron in adults, of which 72% is hemoglobin, 35% is myoglobin, 0.2 is in the form of other compounds, and the rest is reserve iron. Reserve iron accounts for about 25%, which is mainly stored in liver, spleen and bone marrow in the form of ferritin. Adult intake is10-15 mg. Pregnant women need 30mg. 1 month, women lose about twice as much iron as men, and need copper, cobalt, manganese and vitamin C to absorb iron. People in need: women, especially pregnant women, need to supplement iron, but it should be noted that too much iron intake during pregnancy will cause iron poisoning to the fetus. If you are taking anti-inflammatory drugs or must take aspirin every day, then you need to supplement iron. People who often drink black tea or coffee should pay attention to that drinking a lot of black tea and coffee will hinder the absorption of iron.
Iron can be reused during metabolism. Except for intestinal secretion and excretion and exfoliation of skin mucosa epithelium (1mg/ day), almost no other routes lose iron.
The use of iron
In our life, iron can be regarded as the most useful, cheapest, richest and heaviest metal. In industrial and agricultural production, iron is the most important infrastructure material, and ferroalloys are widely used. National defense and war are even more a contest of steel, and the annual output of steel represents the modernization level of a country.
Iron is an indispensable trace element in human body. Among more than ten kinds of trace elements necessary for human body, the importance and quantity of iron rank first. A normal adult's iron content is above 3g, which is equivalent to the quality of a small nail. Hemoglobin in human blood is a complex of iron, which has the functions of oxygen fixation and oxygen transport. Iron deficiency in human body can cause anemia. As long as there is no partial eclipse and no bleeding, adults generally do not lack iron.
The so-called gas poisoning (carbon monoxide poisoning) is also due to the fact that the core of iron atoms in heme is tightly surrounded by carbon monoxide gas molecules, which loses the ability to absorb oxygen molecules and makes people suffocate and die.
Iron is also an indispensable catalyst for plants to produce chlorophyll. If a pot of flowers is short of iron, the flowers will lose their bright colors and refreshing fragrance, and the leaves will turn yellow and wither. Generally speaking, soil also contains many iron compounds. Iron is an important component in soil, and its proportion in soil ranges from less than 1% to more than 20%, with an average of 3.2%. Iron mainly exists in the form of iron oxides, including bivalent iron and trivalent iron, and most iron oxides exist in the form of microcrystals in different degrees in soil particles.
An interesting talk about iron.
People used to think that spinach had high iron content, but it was not.
A scientist found that the iron content of spinach was much smaller than the recorded value. So, he did a lot of experiments and the results were still the same, so he published an article. This article caused a sensation in the whole society, and other scientists conducted experiments one after another and found the same result.
It turns out that when the priest copied the grades, he clicked the wrong decimal point.
Nutritional iron
First, human understanding of iron
Iron deficiency anemia is one of the four major nutritional deficiencies confirmed by the World Health Organization.
In the18th century, Menghini used magnets to absorb particles in dried blood and noticed that blood contained iron.
In 1892, Bunge noticed that infants are prone to iron deficiency.
1928, MacKay proved for the first time that iron deficiency was the cause of the prevalence of infantile anemia in East London. She also believes that providing iron-fortified milk powder can alleviate anemia.
1932, Castle and his colleagues confirmed that inorganic iron can be used for the synthesis of hemoglobin.
Second, the distribution of iron
Iron is an essential trace element for human body. The total amount of iron in human body is 4-5g, which is an important part of hemoglobin. People need it all over their bodies. This mineral already exists in red blood cells that supply oxygen to muscles, and it still needs many enzymes and immune system compounds. The human body takes most of the iron it needs from food, and carefully controls the iron content.
Third, the proper daily intake of human body.
Age of pregnant women, daily intake
0-0.5 years old 0.3mg early 15mg
0.5 years old-1 year old 10mg metaphase 25mg
1-4 years old 12mg late 35mg
4-7 years old 12mg lactation 25mg
7 years old-1 1 year 12mg
1 1 year-old-14 year-old male 16mg female 18mg
14 years old-18 years old male 20mg female 25mg.
18-50 years old male 15mg female 20mg
50 years old 15mg
Fourthly, the physiological function of iron.
1, iron is an important component of hemoglobin, and the function of hemoglobin is to transport oxygen to cells and take carbon dioxide out of cells. The structure of heme and tetraglobulin in hemoglobin provides an effective mechanism, that is, it can combine with oxygen without being oxidized, and plays a key role in the transport of oxygen from lung to tissue.
2. Myoglobin is composed of heme and globulin chains, and exists only in muscle tissue. Its basic function is to transport and store oxygen in muscles.
3. Cytochrome is a series of heme compounds. Through its electron conduction in mitochondria, it has a very important influence on respiration and energy metabolism. For example, cells A, B and C are necessary to generate energy through oxidative phosphorylation.
4. Iron in other iron-containing enzymes can be non-heme iron, NAP dehydrogenase and amber dehydrogenase, which participate in energy metabolism, as well as heme-iron-containing catalase, poly-oxidase (involved in trihydroxy acid cycle), phosphoenolpyruvate kinase (rate-limiting enzyme in sugar production pathway) and nucleotide reductase (enzyme needed for DNA synthesis).
5. Iron catalyzes the transformation of β -carotene into vitamin A, the synthesis of purine and collagen, the production of antibodies, the transport of lipids in blood and the detoxification of drugs in liver. Iron is also closely related to immunity. Studies have shown that iron can improve the body's immunity, increase the phagocytic function of neutrophils and phagocytes, and enhance the body's anti-infection ability.
Verb (abbreviation for verb) lacks symptoms and consequences.
1. Anemia: In severe cases, it can increase the mortality rate of children and mothers and obviously reduce the working ability of the body.
2. Behavior and intelligence: Iron deficiency can cause damage to psychological activities and intellectual development and behavior changes. Iron deficiency (lack before anemia) will also damage children's cognitive ability, and it is difficult to recover after iron supplementation in the future. Animal experiments show that short-term deficiency can reduce the iron content in the brain of young animals. In the future, iron supplementation can correct iron storage in the body, but it has no effect on iron in the brain. Long-term iron deficiency will obviously affect physical endurance. The animal experiments carried out by Finch et al. show that the damage of iron deficiency to the running ability of animals has nothing to do with the level of hemoglobin, but is caused by the damage of muscle oxidative metabolism caused by iron deficiency.
In terms of immunity and anti-infection ability, both human and animal experiments have recorded that one of the characteristics of iron deficiency is the decline of anti-infection ability.
1. In terms of body temperature regulation, another feature of iron deficiency anemia is that the ability to maintain body temperature in a cold environment is impaired.
2. In the aspect of lead poisoning, animal and human experiments have proved that iron deficiency will increase the absorption of lead.
3, some pregnancy consequences, sweaty bowel disease research shows that anemia in early pregnancy is related to premature delivery, low birth weight infants and fetal death.
Symptoms of iron deficiency include pale skin, tongue pain, fatigue or weakness, loss of appetite and nausea.
Effect of iron deficiency on immune system;
1. The ability to resist the invasion of pathogenic microorganisms is weakened.
2. Reduce the reaction speed of immune cells from rest to war.
3. Reduce the activity of antioxidant biochemical enzymes.
4. Antibody production stops or proceeds at a very slow speed.
5. Iron deficiency anemia, insufficient oxygen supply to cells. The result is listless, tired and tired all day, and more susceptible to infection.
Excessive free iron flowing in the blood will not only help to resist and protect the human body, but will be swallowed up by bacteria and become food for bacteria, which will multiply in large numbers. This is why we must be more careful when we supplement iron for our children.
Six, the main food source of iron
Rich in resources: animal blood, liver, chicken gizzard, bovine kidney, soybean, black fungus, sesame paste, beef and mutton, clams and oysters.
Good sources: lean meat, brown sugar, egg yolk, pig kidney, sheep kidney, dried fruits (dried apricots and raisins), beer yeast, seaweed, brown sugar paste and wheat.
General sources: fish, grains, spinach, lentils, peas, mustard leaves, broad beans and melon seeds (pumpkins, zucchini and other seeds).
Trace sources: dairy products, vegetables and fruits.
In addition, cooking tomatoes or other acidic foods in a cast iron pot can also supplement iron, and the pot will put healthy iron into the food.
It seems that many foods contain iron, but China is still a country with serious iron deficiency, mainly women, children and the elderly. Scientific iron supplementation is essential every day!
There are two forms of iron in food:
Nonheme iron. Trivalent iron mainly combines with protein and organic acids to form a complex. This form of iron must be separated from organic matter and reduced to divalent iron before it can be absorbed. If there is more phytic acid or phosphoric acid in the diet, it will form insoluble iron salt with iron, which will affect absorption. Ascorbic acid and cysteine can reduce trivalent iron to divalent iron, which is beneficial to iron absorption.
Iron (Fe) is a component of hemoglobin, myoglobin and many enzymes in the body. Heme iron mainly exists in animal products, which is much better than non-heme iron, which accounts for more than 85% of iron in general diet. However, when ingested with animal protein and vitamins, it can improve the absorption of non-heme iron.
Iron demand, iron metabolism and iron deficiency anemia are discussed in section 127 anemia caused by erythropoiesis deficiency. Section 127 discusses iron-negative diseases.
Iron deficiency can lead to anemia, which is the most common malnutrition in the world. Some infants, adolescent girls and pregnant women suffer from iron deficiency anemia due to insufficient iron intake. Anyone who loses blood will have iron deficiency. All people with iron deficiency need iron supplementation.
Excessive iron poisoning is toxic, which can lead to vomiting, diarrhea and intestinal damage. When a person receives iron treatment for too long or too long, or receives repeated blood transfusions, or has chronic alcoholism, iron will accumulate in the body. Iron deficiency disease (hemochromatosis) is a potentially fatal but treatable hereditary disease, which absorbs too much iron; Affected 1 10,000 Americans.