Iron compounds. Iron: physical and chemical properties

2024 Author: Angel Austin | [email protected]. Last modified: 2024-01-02 17:39

The first products made of iron and its alloys were found during excavations and date back to about the 4th 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 kinds of iron compounds, as well as pure metal, are the most common and used substances. No wonder the 20th century was considered iron. Indeed, before the advent and widespread use of plastic and related materials, it was this compound that was of decisive importance 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 the atom, then first of all we should indicate its location in the periodic system.

Ordinal number - 26.
Period is the fourth big one.
Eighth group, secondary subgroup.
Atomic weight is 55, 847.
The structure of the outer electron shell is indicated by the formula 3d⁶4s^2.
Chemical element symbol - Fe.
Name - iron, reading informula - "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 this atom can 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 metallicity. That is, it is a silvery-white metal with a gray tint, which has 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 0С;
boil - 2862 0C;
activity - medium;
refractory - high;
shows pronounced magnetic properties.

Depending on 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 0C.
From 769 to 917 0C - beta form.
917-1394 0С - gamma form, or austenite.
Over 1394 0S - sigma iron.

All modifications havedifferent types of structure of crystal lattices, and also differ in magnetic properties.

Chemical properties

As mentioned above, the simple substance iron exhibits medium chemical activity. However, in a finely dispersed state, it can ignite spontaneously in air, while the metal itself burns out in pure oxygen.

Corrosion ability is high, so the alloys of this substance are coated with alloying compounds. Iron is able to interact with:

acids;
oxygen (including air);
grey;
halogens;
when heated - with nitrogen, phosphorus, carbon and silicon;
with s alts of less active metals, reducing them to simple substances;
with live steam;
with iron s alts in oxidation state +3.

It is obvious that, showing such activity, the metal is able to form various compounds, diverse and polar in properties. And so it happens. Iron and its compounds are extremely diverse and are used in various branches of science, technology, industrial human activity.

Spread in nature

Natural iron compounds are quite common, because it is the second most abundant element on our planet after aluminum. At the same time, in its pure form, the metal is extremely rare, as part of meteorites, which indicates its large accumulations in space. The main mass is contained in the composition of ores, rocks and minerals.

Ifto talk about the percentage of the element in question in nature, then the following figures can be given.

The cores of the terrestrial planets - 90%.
In the earth's crust - 5%.
In the Earth's mantle - 12%.
In the core of the earth - 86%.
In river water - 2 mg/l.
In the sea and ocean - 0.02 mg/l.

The most common iron compounds form the following minerals:

magnetite;
limonite or brown ironstone;
vivianite;
pyrrhotite;
pyrite;
siderite;
marcasite;
lellingite;
Mispicel;
milanterite and others.

This is far from 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:

cast iron;
steel.

It is also iron that is a valuable addition to many nickel alloys.

Iron(II) compounds

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

oxide;
hydroxide;
binary compounds;
complex s alts;
complex compounds.

The formulas of chemical compounds in which iron exhibits the indicated degree of oxidation are individual for each class. Consider the most important and common of them.

Iron oxide (II). Black powder, insoluble in water. The nature of the connection is basic. It is able to quickly oxidize, however, it can also be easily reduced to a simple substance. It dissolves in acids to form the corresponding s alts. Formula - FeO.

Iron(II) hydroxide. It is a white amorphous precipitate. Formed by the reaction of s alts with bases (alkalis). It shows weak basic properties, is able to quickly oxidize in air to iron compounds +3. Formula - Fe(OH)_2.

S alts of an element in the specified oxidation state. As a rule, they have a pale green color of the solution, oxidize well even in air, acquiring a dark brown color and turning into iron s alts 3. They dissolve in water. Compound examples: FeCL₂, FeSO₄, Fe(NO₃)_2.

Practical value among the designated substances have several compounds. First, iron(II) chloride. This is the main supplier of ions to the human body with anemia. When such an ailment is diagnosed in a patient, 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 vitriol, 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 decade, therefore it is very much appreciated by gardeners and gardeners.

Mora S alt

This connectionwhich is a hydrated iron and ammonium sulfate. Its formula is written as FeSO₄(NH₄)₂SO₄ 6H_{2O. One of the compounds of iron (II), which is widely used in practice. The main areas of human use are as follows.}

Pharmaceuticals.
Scientific research and laboratory titrimetric analyzes (for the determination of chromium, potassium permanganate, vanadium).
Medicine - as an additive to food with a lack of iron in the patient's body.
For the impregnation of wooden products, as Mora s alt protects against decay processes.

There are other areas in which this substance is used. It got its name in honor of the German chemist who first discovered manifested properties.

Substances with iron (III) oxidation state

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. Let's give a description of the main substances.

Iron oxide (III). The powder is fine-crystalline, red-brown in color. It does not dissolve in water, exhibits slightly acidic, more amphoteric properties. Formula: Fe₂O_3.

Iron(III) hydroxide. A substance that precipitates when alkalis react with the corresponding iron s alts. Its character is pronounced amphoteric, the color is brown-brown. Formula: Fe(OH)_3.

S alts, which include the cation Fe³⁺. Many of these have been isolated, with the exception of carbonate, since hydrolysis occurs and carbon dioxide is released. Examples of formulas for some s alts: Fe(NO₃)₃, Fe₂(SO ₄)₃, FeCL_3, FeBr_{3 and others.}

Among the above examples, from a practical point of view, such a crystalline hydrate as FeCL₃6H_{2O, or iron chloride hexahydrate is important (III). It is used in medicine to stop bleeding and replenish iron ions in the body in case of anemia.}

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

Iron(VI) compounds

The formulas of the chemical compounds of iron, where it exhibits a special oxidation state of +6, can be written as follows:

K₂FeO_4;

Na₂FeO_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 them to be used for the treatment of drinking water on an industrial scale.

Complex compounds

Special substances are very important in analytical chemistry and not only. Those that form in aqueous solutions of s alts. These are complex compounds of iron. The most popular and well-researched ones are as follows.

Potassium hexacyanoferrate (II)K₄[Fe(CN)₆]. Another name for the compound is yellow blood s alt. It is used for qualitative determination of Fe³⁺ iron ion in solution. As a result of exposure, the solution acquires a beautiful bright blue color, since another complex is formed - Prussian blue KFe³⁺[Fe²⁺(CN) _{6]. Since ancient times, it has been used as a dye for fabric.}
Potassium hexacyanoferrate (III) K₃[Fe(CN)₆]. Another name is red blood s alt. Used as a qualitative reagent for the determination of iron ion Fe^{2+. As a result, a blue precipitate is formed, which is called Turnbull blue. Also used as fabric dye.}

Iron in 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, on the contrary.

There is one very important organic compound, protein, which includes 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 - breathing - is simply huge.