Iron compounds. Iron: physical and chemical properties

The first products of iron and its alloys were found during excavations and date back to around 4 millennium BC. That is, even the ancient Egyptians and Sumerians used the meteorite deposits of this substance to make jewelry and household items, as well as weapons.

Today, iron compounds of various kinds, as well as pure metal, are the most common and used substances. No wonder the twentieth century was considered to be iron. Indeed, before the advent and wide distribution of plastic and related materials, this connection was of decisive importance for man. What this element is and what substances it forms, we will consider in this article.

The chemical element of iron

If we consider the structure of an atom, we must first of all indicate its locations in the periodic table.

1. The serial number is 26.
2. The period is the fourth big one.
3. Group eight, subgroup secondary.
4. The atomic weight is 55.847.
5. The structure of the outer electron shell is denoted by the formula 3d ⁶ 4s ² .
6. The symbol of the chemical element is Fe.
7. The name is iron, the reading in the formula is ferrum.
8. In nature, there are four stable isotopes of the element under consideration with mass numbers 54, 56, 57, 58.

The chemical element of iron also has about 20 different isotopes that are not stable. The possible oxidation states that a given atom can exhibit:

• 0;
• +2;
• +3;
• +6.

It is important not only the element itself, 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 silvery white with a gray hue of metal, which has a high degree of ductility and plasticity and a high melting point and boiling point. If we consider the characteristics in more detail, then:

• The melting point is 1539 ^° C;
• Boiling - 2862 ^° C;
• Activity - average;
• High refractoriness;
• Exhibits pronounced magnetic properties.

Depending on the conditions and different temperatures, there are several modifications that form iron. Their physical properties differ from the fact that the crystal lattices differ.

1. The alpha-form, or ferrite, exists up to a temperature of 769 ^° C.
2. From 769 to 917 ⁰ C is the beta form.
3. 917-1394 ⁰ C - gamma form, or austenite.
4. Over 1394 ⁰ С - sigma-iron.

All modifications have different types of crystal lattice structure, and also differ in magnetic properties.

Chemical properties

As already mentioned above, a simple substance, iron exhibits an average chemical activity. However, in a fine-dispersed state it is capable of self-igniting in air, and in pure oxygen, the metal itself burns.

Corrosivity is high, so alloys of this substance are coated with doping 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, restoring them to simple substances;
• With hot water vapor;
• With iron salts in oxidation state +3.

Obviously, in manifesting 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 the most diverse branches of science, technology, and industrial activity of man.

Distribution in nature

Natural iron compounds occur quite often, because this is the second most common element on our planet after aluminum. In this pure metal is extremely rare, in the composition of meteorites, which indicates its large clusters in space. The main mass is contained in the composition of ores, rocks and minerals.

If we talk about the percentage content of the element in question in nature, the following figures can be cited.

1. The core of the terrestrial planets is 90%.
2. In the earth's crust - 5%.
3. In the mantle of the Earth - 12%.
4. In the Earth's core - 86%.
5. In the river water - 2 mg / l.
6. In the sea and ocean - 0,02 mg / l.

The most common iron compounds form the following minerals:

• magnetite;
• Limonite or brown iron ore;
• Vivianite;
• Pyrrhotite;
• pyrite;
• siderite;
• Marcasite;
• Lellingitis;
• Misikel;
• Milanterite and others.

This is still far from a complete list, because they are really very many. In addition, various alloys that are created by man are widely distributed. These are also such compounds of iron, without which it is difficult to imagine the modern life of people. There are two main types:

• Cast iron;
• become.

Also, iron is a valuable additive in the composition of many nickel alloys.

The compounds of iron (II)

These include those in which the oxidation state of the forming element is +2. They are quite numerous, because they include:

• oxide;
• Hydroxide;
• Binary connections;
• Complex salts;
• Complex compounds.

Formulas of chemical compounds in which iron exhibits this degree of oxidation are individual for each class. Consider the most important and common ones.

1. Iron oxide (II). The powder is black, it does not dissolve in water. The nature of the connection is basic. It is able to rapidly oxidize, however it can also be easily restored to a simple substance. It dissolves in acids, forming the corresponding salts. The formula is FeO.
2. Ferric hydroxide (II). It is a white amorphous precipitate. Formed by the reaction of salts with bases (alkalis). It exhibits weak basic properties, is able to rapidly oxidize in air to iron compounds +3. The formula is Fe (OH) ₂ .
3. The salts of the element in the indicated oxidation state. They usually have a pale green color of the solution, they oxidize well even in air, becoming dark brown and turning into iron salts. 3. Dissolve in water. Examples of compounds: FeCL ₂ , FeSO ₄ , Fe (NO ₃ ) ₂ .

Practical significance among the indicated substances have several compounds. First, iron (II) chloride. It is the main supplier of ions to the human body, anemic patient. When such an ailment is diagnosed in a patient, then complex preparations based on the compound under consideration are prescribed for it. This is how iron deficiency is replenished in the body.

Secondly, iron vitriol, that is ferrous sulfate (II), together with copper is used to destroy agricultural pests in crops. The method proves its effectiveness not for the first ten years, therefore it is very appreciated by gardeners and truck farmers.

The Mora salt

This compound, which is the crystal hydrate of ferrous sulfate and ammonium. Its formula is written as FeSO ₄ * (NH ₄ ) ₂ SO ₄ * 6H ₂ O. One of the iron (II) compounds, which has been widely used in practice. The main areas of human use are as follows.

1. Pharmaceuticals.
2. Scientific research and laboratory titrimetric analyzes (for determining the content of chromium, potassium permanganate, vanadium).
3. Medicine - as an additive to food with a lack of iron in the patient's body.
4. For the impregnation of wooden products, since Mohr's salt protects against decay processes.

There are other areas in which this substance finds application. Its name it received in honor of a German chemist who first discovered the manifested properties.

Substances with a degree of oxidation of iron (III)

The properties of iron compounds in which it exhibits +3 oxidation degree are somewhat different from those considered above. Thus, the character of the corresponding oxide and hydroxide is no longer basic, but pronounced amphoteric. Let's describe the main substances.

1. Iron oxide (III). The powder is small-crystalline, red-brown in color. In water it does not dissolve, it exhibits weakly acidic properties, more amphoteric. Formula: Fe ₂ O ₃ .
2. Ferric hydroxide (III). A substance precipitated by the action of alkalis on the corresponding iron salts. Its character is pronounced amphoteric, the color is brownish-brown. Formula: Fe (OH) ₃ .
3. Salts, which include the cation of Fe ³⁺ . Such a set is distinguished, except for the carbonate, since hydrolysis occurs and carbon dioxide is released. Examples of formulas of some 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, an important crystalline hydrate, such as FeCL _{3 *} 6H ₂ O, or iron (III) hexahydrochloride is important. It is used in medicine to stop bleeding and replenish iron ions in the body with anemia.

Nine-ferric iron (III) sulphate is used to purify drinking water, as it behaves like a coagulant.

The compounds of iron (VI)

Formulas of chemical compounds of iron, where it exhibits a special degree of oxidation +6, can be written as follows:

• K ₂ FeO ₄ ;
• Na ₂ FeO ₄ ;
• MgFeO ₄ and others.

They all have a common name - ferrates - and have similar properties (strong reducing agents). They are also capable of disinfecting and have a bactericidal effect. This allows them to be used for treatment of drinking water on an industrial scale.

Complex compounds

Very important in analytical chemistry and not only are special substances. Such that are formed in aqueous solutions of salts. These are complex iron compounds. The most popular and well-studied ones are as follows.

1. Hexacyanoferrate (II) potassium K ₄ [Fe (CN) ₆ ]. Another name for the compound is yellow blood salt. It is used for the qualitative determination of iron Fe ³⁺ in solution. As a result of the action, the solution acquires a beautiful bright blue color, as another complex is formed-the Berlin blue of KFe ³⁺ [Fe ²⁺ (CN) ₆ ]. Since ancient times it has been used as a dye for fabric.
2. Hexacyanoferrate (III) potassium K ₃ [Fe (CN) ₆ ]. Another name is red blood salt. It is used as a qualitative reagent to determine the Fe ²⁺ iron ^ion . As a result, a blue precipitate is formed, called the turbulence blue. Also used as a dye for fabric.

Iron in the composition of organic substances

Iron and its compounds, as we have already seen, are of great practical importance in the economic life of man. However, in addition, his biological role in the body is no less great, even on the contrary.

There is one very important organic compound, a protein, into which this element belongs. This is hemoglobin. It is thanks to him that oxygen is transported and a uniform and timely gas exchange is carried out. Therefore, the role of iron in a vital process - breathing - is simply enormous.

In total, about 4 grams of iron are contained within the human body, which must be constantly replenished by consumed food.