It is difficult to overestimate the role of iron for the human body, because it contributes to the "creation" of blood, its content affects the level of hemoglobin and myoglobin, iron normalizes the enzyme system. But what is this element in terms of chemistry? What is the valence of iron? This will be discussed in this article.
A bit of history
Mankind knew about this chemical element and even owned products from it back in the 4th century BC. These were the peoples of Ancient Egypt and the Sumerians. It was they who first began to make jewelry, weapons from an alloy of iron and nickel, which were found during archaeological excavations and carefully studied by chemists.
A little later, the Aryan tribes who moved to Asia learned to extract solid iron from ore. It was so valuable to people of that time that the items were covered with gold!
Iron characteristic
Iron (Fe) ranks fourth in terms of its content in the bowels of the earth's crust. It takes place in group 7 of period 4 and has number 26 in the chemical table of Mendeleev’s elements. The valency of iron is directly dependent on its position in the table. But more on that later.
This metal is most common in nature in the form of ore, found in water as a mineral, as well as in various compounds.
The largest amount of iron reserves in the form of ore is in Russia, Australia, Ukraine, Brazil, the USA, India, and Canada.
Physical properties
Before proceeding to the valency of iron, it is necessary to consider in more detail its physical properties, so to speak, to look closer at it.
This metal has a silver color, sufficiently ductile, but is capable of increasing hardness by its interaction with other elements (for example, carbon). It also has magnetic properties.
In a humid environment, iron can corrode, that is, rust. Although absolutely pure metal is more resistant to moisture, but if it contains impurities, it is they that provoke corrosion.
Iron interacts well with the acidic environment, it can even form salts of ferric acid (subject to a strong oxidizing agent).
In air, it quickly becomes coated with an oxide film, which protects it from interactions.
Chemical properties
Also, this element has a number of chemical properties. Iron, like the other elements of the periodic table, has an atomic nucleus charge, which corresponds to the ordinal number +26. And 26 electrons rotate near the nucleus.
In general, if we consider the properties of iron - a chemical element, then it is a metal with a low active ability.
Interacting with weaker oxidizing agents, iron forms compounds where it is divalent (that is, its oxidation state is +2). And if with strong oxidizing agents, then the degree of oxidation of iron reaches +3 (that is, its valency becomes equal to 3).
When interacting with chemical elements that are not metals, Fe acts as a reducing agent in relation to them, while its oxidation state becomes, in addition to +2 and +3, even +4, +5, +6. Such compounds have very strong oxidizing properties.
As noted above, iron in the air is coated with an oxide film. And when heated, the reaction rate increases and iron oxide with valency 2 (temperature less than 570 degrees Celsius) or oxide with valency 3 (temperature indicator more than 570 degrees) can form.
The interaction of Fe with halogens leads to the formation of salts. The elements fluorine and chlorine oxidize it to +3. But bromine is up to +2 or +3 (it all depends on what are the conditions for the chemical transformation to occur when interacting with iron).
Entering into interaction with iodine, the element is oxidized to +2.
By heating iron and sulfur, iron sulfide with a valency of 2 is obtained.
If the ferrum is melted and combined with carbon, phosphorus, silicon, boron, nitrogen, then compounds called alloys are obtained.
Iron is a metal, therefore, it also interacts with acids (this was also briefly discussed a little higher). For example, sulfuric and nitric acids, which have a high concentration, in an environment with a low temperature, do not affect iron. But if she rises, the reaction takes place, as a result of which the iron is oxidized to +3.
The higher the acid concentration, the higher the temperature must be given.
Heating 2-valent iron in water, we get its oxide and hydrogen.
Fe also has the ability to displace metals from aqueous solutions of salts that have a reduced activity. Moreover, it oxidizes to +2.
With increasing temperature, iron reduces metals from oxides.
What is valency?
Already in the previous section, the concept of valency, as well as the degree of oxidation, was slightly encountered. It's time to consider the valency of iron.
But first you need to understand what kind of chemical element property it is.
Chemicals are almost always constant in their composition. For example, in the H2O water formula - 1 oxygen atom and 2 hydrogen atoms. The same is true with other compounds in which two chemical elements are involved, one of which is hydrogen: 1-4 hydrogen atoms can be added to the 1 atom of the chemical element. But not the other way around! And therefore, it is clear that hydrogen attaches to itself only 1 atom of another substance. And this phenomenon is called valency - the ability of atoms of a chemical element to attach a specific number of atoms of other elements.
Valency value and graphic formula
There are elements of the periodic table that have a constant valency - these are oxygen and hydrogen.
And there are such chemical elements in which it changes. For example, iron is more often than 2 and 3 valence, sulfur 2, 4, 6, carbon 2 and 4. These are elements with variable valency.
Further, understanding what valency is, you can correctly write the graphic formula of the compounds. It displays the sequence of compounds of atoms in a molecule.
Also, knowing the valency of one of the elements in the compound, one can determine the valency of the other.
Iron valency
As noted, iron refers to elements with variable valency. And it can fluctuate not only between indicators 2 and 3, but also reach 4, 5 and even 6.
Of course, inorganic chemistry studies the valency of iron in more detail . Let us consider this mechanism briefly at the level of the simplest particles.
Iron is a d-element, to which another 31 elements of the periodic table are assigned (these are 4-7 periods). With an increase in the serial number, the properties of d-elements acquire small changes. The atomic radius of these substances also increases slowly. They have a variable valency, which depends on the fact that the pre-entry d-electron sublevel is incomplete.
Therefore, for iron, valence is not only c-electrons in the outer layer, but also unpaired 3D electrons of the outer layer. And, as a result, the valency of Fe in chemical compounds can be 2, 3, 4, 5, 6. Basically, it is 2 and 3 - these are more stable compounds of iron with other substances. In less stable ones, it exhibits a valency of 4, 5, 6. But, such compounds are less common.
Divalent Ferrum
The interaction of 2 valence iron with water produces iron oxide (2). This compound is black. Easily interacts with hydrochloric (low concentration) and nitric (high concentration) acids.
If such a 2-valent iron oxide is reacted with either hydrogen (temperature 350 degrees Celsius) or carbon (coke) at 1000 degrees, then it is restored to a pure state.
2-valent iron oxide is obtained in the following ways:
- through the connection of oxide of 3-valent iron with carbon monoxide;
- when heating pure Fe, with a low oxygen pressure;
- when unfolding 2-valent iron oxalate in a vacuum environment;
- in the interaction of pure iron with its oxides, the temperature is 900-1000 degrees Celsius.
As for the natural environment, iron oxide of 2 valence is present in the form of the wustite mineral.
There is another way, how to determine the valency of iron in a solution - in this case, having its index of 2. It is necessary to carry out reactions with the red salt (potassium hexacyanoferrate) and with alkali. In the first case, a precipitate of a dark blue color is obtained - a complex salt of iron of 2 valence. In the second, a dark gray-green precipitate is obtained - iron hydroxide also of 2 valence, while iron 3-valence has a dark brown color in the solution.
Ferric iron
3-valence ferrum oxide has a powdery structure, the color of which is red-brown. It also has the following names: iron oxide, iron minium, red pigment, food coloring, crocus.
In nature, this substance is found in the form of a mineral - hematite.
The oxide of such iron does not interact with water. But it connects with acids and alkalis.
Iron oxide is used (3) for coloring materials used in construction:
- bricks;
- cement;
- ceramic products;
- concrete;
- paving slabs;
- floor coverings (linoleum).
Iron in the human body
As noted at the beginning of the article, the substance iron is an important component of the human body.
When this element is not enough, the following consequences may occur:
- increased fatigue and sensitivity to cold;
- dry skin
- decreased brain activity;
- deterioration of the strength of the nail plate;
- dizziness;
- digestion problems;
- gray hair and hair loss.
Iron builds up, usually in the spleen and liver, as well as in the kidneys and pancreas.
In the human diet should be products containing iron:
- beef liver;
- buckwheat porridge;
- peanut;
- pistachios;
- canned green peas;
- dried porcini mushrooms;
- chicken eggs;
- spinach;
- dogwood;
- apples
- pears
- peaches;
- beet;
- seafood.
A lack of iron in the blood leads to a decrease in hemoglobin and the development of a disease such as iron deficiency anemia.