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 functioning of the enzyme system. But what is this element in terms of chemistry? What is the valency 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 as early as 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 examined by chemists.
A little later, the tribes of the Aryans who moved to Asia learned how to extract solid iron from ore. It was so valuable for the people of that time that the products were covered with gold!
Iron characteristics
Iron (Fe) is in fourth place in terms of its content in the bowels of the earth's crust. It occupies a place in the 7th group of the 4th period and has the number 26 inchemical table of elements of Mendeleev. 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 iron ore reserves are in Russia, Australia, Ukraine, Brazil, USA, India, Canada.
Physical properties
Before moving on to the valency of iron, it is necessary to take a closer look at its physical properties, so to speak, take a closer look at it.
This metal has a silvery color, is quite ductile, but is capable of increasing hardness through its interaction with other elements (for example, with 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 acidic environments, it can even form s alts of iron acid (provided a strong oxidizing agent).
In air, it quickly becomes covered with an oxide film that protects it from interactions.
Chemical properties
Also, this element has a number of chemical properties. Iron, like the rest of the elements of the periodic table, has the charge of the atomic nucleus, which corresponds to the serial number +26. And around the nucleus, 26 electrons rotate.
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 oxidation state of iron reaches +3 (that is, its valence 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 covered with an oxide film. And when heated, the reaction rate increases and iron oxide with valence 2 (temperature less than 570 degrees Celsius) or oxide with valence 3 (temperature index more than 570 degrees) can be formed.
Interaction of Fe with halogens leads to the formation of s alts. The elements fluorine and chlorine oxidize it to +3. Bromine is up to +2 or +3 (it all depends on the conditions for the implementation of a chemical transformation when interacting with iron).
Interacting with iodine, the element is oxidized to +2.
Heating iron and sulfur produces iron sulfide with a valence of 2.
If you melt ferrum and combine it with carbon, phosphorus, silicon, boron, nitrogen, you get compounds called alloys.
Iron is a metal,therefore, it also interacts with acids (this was also briefly discussed a little higher). For example, sulfuric and nitric acids, having a high concentration, in an environment with a low temperature, do not affect iron. But as soon as it rises, a reaction occurs, as a result of which iron is oxidized to +3.
The higher the acid concentration, the higher the temperature should be given.
Heating 2-valent iron in water, we get its oxide and hydrogen.
Also, Fe has the ability to displace metals that have reduced activity from aqueous solutions of s alts. At the same time, it is oxidized to +2.
When the temperature rises, iron restores metals from oxides.
What is valence
Already in the previous section, the concept of valence, as well as the degree of oxidation, was encountered a little. It's time to consider the valency of iron.
But first you need to understand what kind of property of chemical elements it is.
Chemical substances are almost always constant in their composition. For example, in the formula for water H2O - 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 1 atom of a chemical element. But not vice versa! Therefore, it is clear that hydrogen attaches only 1 atom of another substance to itself. And it is this phenomenon that is called valency - the ability of atoms of a chemical element to attach a specificthe number of atoms of other elements.
Valence value and graphical formula
There are elements of the periodic table that have a constant valence - these are oxygen and hydrogen.
And there are chemical elements in which it changes. For example, iron is more often 2 and 3 valent, sulfur 2, 4, 6, carbon 2 and 4. These are elements with variable valency.
Further, understanding what valency is, you can correctly write the graphical formula of compounds. It displays the sequence of connection of atoms in a molecule.
Also, knowing the valency of one of the elements in the compound, you 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 2 and 3, but also reach 4, 5 and even 6.
Of course, inorganic chemistry studies iron valency in more detail. Let us briefly consider this mechanism at the level of the simplest particles.
Iron is a d-element, to which 31 more elements of the periodic table are added (these are 4-7 periods). As the atomic number increases, the properties of the d-elements acquire slight changes. The atomic radius of these substances also slowly increases. They have a variable valence, which depends on the fact that the pre-outer d-electron sublevel is incomplete.
Because for iron, not only c-electrons located in the outer layer are valence, but also unpaired 3d-electrons of the pre-outer layer. And, as a consequence, the valency of Fe in chemicalcompounds can be equal to 2, 3, 4, 5, 6. Basically, it is equal to 2 and 3 - these are more stable compounds of iron with other substances. In less stable ones, it exhibits valency 4, 5, 6. But, such compounds are less common.
Bivalent ferrum
When 2 valence iron interacts with water, iron oxide (2) is obtained. This connection is black. Reacts quite easily with hydrochloric (low concentration) and nitric (high concentration) acids.
If such an oxide of 2-valent iron interacts with either hydrogen (temperature 350 degrees Celsius) or carbon (coke) at 1000 degrees, then it is restored to a pure state.
Extract ferrous oxide of 2-valent iron in the following ways:
- through the combination of ferrous oxide with carbon monoxide;
- when pure Fe is heated, while oxygen pressure is low;
- when decomposing ferrous oxalate in a vacuum environment;
- when pure iron interacts with its oxides, the temperature is 900-1000 degrees Celsius.
As for the natural environment, ferric oxide is divalent, present as the mineral wuestite.
There is another way to determine the valence of iron in a solution - in this case, having its index 2. It is necessary to carry out reactions with red s alt (potassium hexacyanoferrate) and with alkali. In the first case, a dark blue precipitate is observed - a complex s alt of ferric 2-valent. Inthe second - obtaining a dark gray-green precipitate - iron hydroxide is also 2-valent, while 3-valent iron hydroxide has a dark brown color in solution.
Trivalent iron
3-valent ferrum oxide has a powder structure, the color of which is red-brown. It also has the names: iron oxide, iron minium, red pigment, food coloring, crocus.
In nature, this substance occurs in the form of a mineral - hematite.
The oxide of such iron no longer interacts with water. But it combines with acids and alkalis.
Iron oxide (3) is used to color materials used in construction:
- bricks;
- cement;
- ceramic products;
- concrete;
- paving slabs;
- flooring (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 insufficient, 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;
- grey hair and hair loss.
Iron accumulates, usually in the spleen and liver, as well as the kidneys and pancreas.
The human diet should contain foods containing iron:
- beef liver;
- buckwheat porridge;
- peanuts;
- pistachios;
- canned green peas;
- dried porcini mushrooms;
- chicken eggs;
- spinach;
- dogwood;
- apples;
- pears;
- peaches;
- beets;
- seafood.
Lack of iron in the blood leads to a decrease in hemoglobin and the development of a disease such as iron deficiency anemia.
