The first products from iron and its alloys were found during excavations and date back to about 4 millennium BC. That is, even the ancient Egyptians and Sumerians used meteorite deposits of this substance to make jewelry and household items, as well as weapons.
Today, various types of iron compounds, as well as pure metal, are the most common and used substances. No wonder the XX century was considered the iron. Indeed, before the appearance and widespread use of plastic and related materials, it was this compound that was crucial for humans. What is this element and what substances it forms, we will consider in this article.
Chemical element iron
If we consider the structure of an atom, then first of all it is necessary to indicate its location in the periodic system.
- The serial number is 26.
- The period is the fourth big.
- Group eight, subgroup secondary.
- Atomic weight - 55.847.
- The structure of the outer electron shell is indicated by the formula 3d 6 4s 2 .
- The symbol of the chemical element is Fe.
- The name is iron, the reading in the formula is "ferrum".
- In nature, there are four stable isotopes of the element in question with mass numbers 54, 56, 57, 58.
The chemical element iron also has about 20 different isotopes that are not stable. Possible oxidation states that a given atom may exhibit:
Not only the element itself is important, but also its various compounds and alloys.
Physical properties
As a simple substance, iron has physical properties with pronounced metallism. That is, it is a silver-white with a gray tint metal with a high degree of ductility and ductility and a high melting and boiling point. If we consider the characteristics in more detail, then:
- melting point - 1539 0 C;
- boiling - 2862 0 C;
- activity - medium;
- refractoriness - high;
- exhibits pronounced magnetic properties.
Depending on the conditions and different temperatures, there are several modifications that iron forms. Their physical properties differ from the fact that the crystal lattices differ.
- The alpha form, or ferrite, exists up to a temperature of 769 0 C.
- From 769 to 917 0 C is a beta form.
- 917-1394 0 C - gamma form, or austenite.
- Over 1394 0 C - sigma-iron.
All modifications have different types of crystal lattice structures, and also differ in magnetic properties.
Chemical properties
As mentioned above, a simple substance, iron, exhibits moderate chemical activity. However, in a finely dispersed state it is capable of self-igniting in air, and in pure oxygen the metal itself burns.
Corrosion is high, so the alloys of this substance are coated with alloying compounds. Iron is able to interact with:
- acids;
- oxygen (including air);
- gray;
- halogens;
- when heated, with nitrogen, phosphorus, carbon and silicon;
- with salts of less active metals, reducing them to simple substances;
- with sharp water vapor;
- with iron salts in oxidation state +3.
It is obvious that, showing such activity, the metal is able to form various compounds, diverse and polar in properties. This is what happens. Iron and its compounds are extremely diverse and find application in various fields of science, technology, and human industrial activity.
Spread in nature
Natural iron compounds are quite common, because it is the second most abundant element on our planet after aluminum. Moreover, in its pure form, metal is extremely rare in meteorites, which indicates its large clusters in space. The bulk is contained in the composition of ores, rocks and minerals.
If we talk about the percentage of the element in nature, then the following figures can be given.
- Nuclei of the terrestrial planets - 90%.
- In the earth's crust - 5%.
- In the mantle of the Earth - 12%.
- In the earth’s core - 86%.
- In river water - 2 mg / l.
- In sea and ocean - 0.02 mg / l.
The most common iron compounds form the following minerals:
- magnetite;
- limonite or brown iron ore;
- vivianite;
- pyrrhotite;
- pyrites;
- siderite;
- marcasite;
- Lellingitis
- mispickel;
- milanteritis and others.
This is not a complete list, because there are really a lot of them. In addition, various alloys that are created by man are widespread. These are also such iron compounds, without which it is difficult to imagine the modern life of people. These include two main types:
Also, iron is a valuable additive in the composition of many nickel alloys.
Iron (II) compounds
These include those in which the oxidation state of the generatrix element is +2. They are quite numerous, because they include:
- oxide;
- hydroxide;
- binary compounds;
- complex salts;
- complex compounds.
Formulas of chemical compounds in which iron exhibits the indicated oxidation state are individual for each class. Consider the most important and common of them.
- Iron oxide (II). The powder is black, does not dissolve in water. The nature of the connection is basic. It is able to oxidize quickly, however, it can also be easily reduced to a simple substance. It dissolves in acids, forming the corresponding salts. The formula is FeO.
- Iron hydroxide (II). It is a white amorphous precipitate. It is formed during the reaction of salts with bases (alkalis). It exhibits weak basic properties, is able to quickly oxidize in air to iron compounds +3. The formula is Fe (OH) 2 .
- Salts of the element in the specified oxidation state. As a rule, they have a pale green color of the solution, they are well oxidized even in air, becoming dark brown and turning into iron salts 3. They dissolve in water. Examples of compounds: FeCL 2 , FeSO 4 , Fe (NO 3 ) 2 .
Among the designated substances, several compounds are of practical importance. Firstly, iron (II) chloride . It is the main supplier of ions to an anemic person. When such an ailment is diagnosed in a patient, then he is prescribed complex preparations, which are based on the compound in question. This is how iron deficiency in the body is replenished.
Secondly, iron sulfate, that is, iron (II) sulfate, together with copper is used to destroy agricultural pests in crops. The method has been proving its effectiveness for more than a dozen years, therefore it is very appreciated by gardeners and gardeners.
Salt Mora
This is a compound that is an iron and ammonium sulfate crystalline hydrate. Its formula is written as FeSO 4 * (NH 4 ) 2 SO 4 * 6H 2 O. One of the compounds of iron (II), which has been widely used in practice. The main areas of human use are as follows.
- Pharmaceuticals
- Scientific research and laboratory titrimetric analyzes (to determine the content of chromium, potassium permanganate, vanadium).
- Medicine - as an additive to food with a lack of iron in the patient's body.
- For impregnation of wooden products, as Mora salt protects from rotting processes.
There are other areas in which this substance is used. It received its name in honor of a German chemist who first discovered the manifested properties.
Substances with oxidation state of iron (III)
The properties of iron compounds in which it exhibits an oxidation state of +3 are somewhat different from those discussed above. Thus, the nature of the corresponding oxide and hydroxide is no longer basic, but pronounced amphoteric. We give a description of the main substances.
- Iron oxide (III). The powder is crystalline, reddish-brown. It does not dissolve in water, exhibits slightly acidic properties, more amphoteric. Formula: Fe 2 O 3 .
- Iron (III) hydroxide. A substance which precipitates when alkalis act on the corresponding iron salts. Its nature is pronounced amphoteric, the color is brown-brown. Formula: Fe (OH) 3 .
- Salts, which include the cation Fe 3+ . There are many of them, with the exception of carbonate, since hydrolysis occurs and carbon dioxide is released. Examples of formulas of certain salts: Fe (NO 3 ) 3 , Fe 2 (SO 4 ) 3 , FeCL 3, FeBr 3 and others.
Among the examples given, from a practical point of view, such a crystalline hydrate as FeCL 3 * 6H 2 O or hexahydrate iron (III) chloride is of great importance. It is used in medicine to stop bleeding and replenish iron ions in the body with anemia.
Nine-water iron (III) sulfate is used to purify drinking water, as it behaves like a coagulant.
Iron (VI) compounds
Formulas of chemical compounds of iron, where it exhibits a special oxidation state of +6, can be written as follows:
- K 2 FeO 4 ;
- Na 2 FeO 4 ;
- MgFeO 4 and others.
All of them have a common name - ferrates - and have similar properties (strong reducing agents). They are also able to disinfect and have a bactericidal effect. This allows you to use them for the treatment of drinking water on an industrial scale.
Complex compounds
Very important in analytical chemistry and not only are special substances. Those that form in aqueous solutions of salts. These are complex compounds of iron. The most popular and well-studied of them are as follows.
- Potassium hexacyanoferrate (II) K 4 [Fe (CN) 6 ]. Another name for the compound is yellow blood salt. It is used for the qualitative determination of Fe 3+ in a solution of iron ion. As a result of exposure, the solution acquires a beautiful bright blue color, since another complex is formed - Prussian blue KFe 3+ [Fe 2+ (CN) 6 ]. From ancient times used as a dye for fabrics.
- Potassium hexacyanoferrate (III) K 3 [Fe (CN) 6 ]. Another name is red blood salt. It is used as a qualitative reagent for the determination of iron ion Fe 2+ . As a result, a blue precipitate is formed, called Turnbull blue. Also used as a dye for fabrics.
Iron as part of organic matter
Iron and its compounds, as we have seen, are of great practical importance in the economic life of man. However, in addition to this, its biological role in the body is no less great, even vice versa.
There is one very important organic compound, the protein, which contains this element. This is hemoglobin. It is thanks to him that oxygen is transported and uniform and timely gas exchange is carried out. Therefore, the role of iron in the vital process - respiration - is simply enormous.
In total, about 4 grams of iron is contained inside the human body, which must be constantly replenished due to the consumed food.