It is Difficult to overestimate the role of iron for the human body because it promotes a “creation” of the blood, it affects the level of hemoglobin and myoglobin, iron normalizes enzyme system. But what is this element from the point of view of chemistry? What is the valence of iron? This will be discussed in this article.
Humanity knew about this element and even owned the products in the fourth century BC. It was the peoples of Ancient Egypt and the Sumerians. They first began to make jewelry, and weapons from an alloy of iron and Nickel, which were found during archaeological excavations have been thoroughly investigated by chemists.
A Little later, the Aryan tribes who moved to Asia, learned to produce solid iron from iron ore. It was so valuable to the people of that time that the products were covered with gold!
Iron (Fe) is the fourth place for its content in the earth's crust. It takes place in the 7 group 4 and period is number 26 in the chemical table of the elements. The valence of iron is directly dependent on their position in the table. But more on that later.
This metal is most likely distributed in nature in the form of ore, is found in water as a mineral and in various combinations.
The Largest number of stocks of iron in the ore is found in Russia, Australia, Ukraine, Brazil, USA, India, Canada.
Before proceeding to the valence of iron, it is necessary to elaborate its physical properties, so to speak, to look at it closer.
This metal has a silvery color, rather plastic, but is capable of increasing the hardness through its interaction with other elements (e.g. carbon). It also has magnetic properties.
In the damp environment, the iron may corrode, that is rusting. While it is pure metal more resistant to moisture, but if there are impurities, they provoke corrosion.
Iron interacts well with the acidic environment, even able to form the iron salt of the acid (a strong oxidizer).
In the air quickly covered with an oxide film which protects it from interactions.
Also, this element has several chemical properties. Iron, like other elements of the periodic table, has the charge of the atomic nucleus, which corresponds to the sequence number +26. And near the nucleus rotates 26 electrons.
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In General, if we consider the properties of iron – a chemical element is a metal with a low active ability.
Interacting with the weaker oxidizing agents, iron forms compounds where it is divalent (i.e., its oxidation state +2). But if with strong oxidizing agents, the oxidation state of iron is +3 (i.e. its valence is equal to 3).
During the interaction with chemical elements that are not metals, Fe acts in relation to them, reducing, thus, the degree of oxidation to be, in addition to the +2 and +3, even +4, +5, +6. Such compounds are very strong oxidizing properties.
As mentioned above, iron in the air covered with an oxide film. But when heated, the reaction rate increases and may form the iron oxide with valence of 2 (temperature less than 570 degrees Celsius) or oxide with a valence of 3 (thermal index of more than 570 degrees).
The Interaction of Fe with Halogens leads to the formation of salts. The elements fluorine and chlorine oxidize it to +3. Bromine is the same – to +2 or +3 (all depends on the conditions of implementation of the chemical transformations during the interaction with iron).
Entering into interaction with iodine, the element is oxidized to +2.
By Heating iron and sulfur, iron sulfide is obtained with a valence of 2.
If ferrum to melt and combine with carbon, phosphorus, silicon, boron, nitrogen, you get compounds called alloys.
Iron is a metal, so it reacts with acids (this is also briefly mentioned just above). For example, acids of sulphur and nitrogen, having a high concentration, in an environment with low temperature, the iron does not have an impact. But it's worth it will increase as the reaction occurs, in which iron is oxidized to +3.
The higher the concentration of acid, the greater the temperature needed to give.
Heating 2-valent iron in water, will receive its oxide and hydrogen.
Also, the Fe has the ability to displace aqueous solutions of salts of metals which have a reduced activity. In this case it is oxidized to +2.
When the temperature rises, the iron recovers the metals from the oxides.
Already in the previous section a bit the concept of valence and oxidation States. It's time to consider the valence of iron.
But first we need to understand what kind of a property of chemical elements.
The Chemicals are almost always permanent in its composition. For example, in the formula of water H2O – 1oxygen atom and 2 hydrogen atoms. It's the same with other connections that involve two chemicals, one of which is the hydrogen to 1 atom of a chemical element can be added 1-4 hydrogen atoms. But not Vice versa! Therefore, it is seen that the hydrogen attaches to only 1 atom of another substance. And this phenomenon is called the valence-ability of atoms of a chemical element to attach a specific number of atoms of other elements.
There are elements of the periodic table, which have a constant valency-oxygen and hydrogen.
And there are chemical elements, which it changes. For example, iron often 2-and 3-valent sulfur 2, 4, 6, carbon 2 and 4. these are elements with variable valence.
Next, understand what the valence, it is possible to write the graphical formula of the compounds. It displays the sequence of connection of atoms in the molecule.
Also, knowing the valence of one of the elements in the compound, it is possible to determine the valence of the other.
As noted, the iron belongs to the elements with variable valence. And it can vary not only between figures 2 and 3, but also to achieve 4, 5 and even 6.
Of Course, more studies the valence of iron is inorganic chemistry. Let us consider briefly the mechanism at the level of elementary particles.
Iron is a d-element, which is ranked 31 in the element of the periodic table (it is 4-7 periods). With increasing sequence numbers, properties of d-elements have small changes. The atomic radius of these substances are also slowly increasing. They possess a variable valence, which depends on what predvneshnem d electronic sublevel is a work in progress.
Because the valence of iron is not only s-electrons in the outer layer, but the unpaired 3D-electrons predvneshnem layer. And, as a consequence, the Fe valence in chemical compounds can be infinite 2, 3, 4, 5, 6. Basically, it is equal to 2 and 3 – this is a more stable compounds of iron with other substances. In less steady - he has valence 4, 5, 6. But, such connections are less common.
In the interaction of 2 valent iron with water it turns iron oxide (2). Such a connection has in black. Quite easily interacts with the salt (low concentrations) and nitrogen (high concentration) acids.
If this oxide 2-valent iron to interact or hydrogen (350 degrees Celsius), or with carbon (coke) at 1000 degrees, it is restored to a clean state.
Mined iron oxide 2-valent ways:
With regard to the natural environment, the iron oxide 2-valent is present in the form of mineral wustite.
There is another way, as in the solution to determine the valence of iron – in this case with the figure 2. It is necessary to conduct the reaction with red salt (hexacyanoferrate potassium) and alkali. In the first case there is obtaining a precipitate of dark-blue color – iron complex salts of 2-valent. In the second – obtaining a dark gray-green sludge – iron hydroxide 2-valent, at that time, as the iron hydroxide 3-valent has a color in the solution is dark brown.
Oxide of 3-valent ferrum has a powdery structure, the color of which is red-brown. Also has names: iron oxide, iron minium, a red pigment, food coloring, Crocus.
In nature, this substance is found in the form of mineral-hematite.
Oxide of iron with water has not interact. But unites with acids and alkalis.
Used iron oxide (3) for coloring materials used in construction:
As mentioned in the beginning of the article, the substance of iron is an important component of the human body.
When this element is not enough, you may experience the following consequences:
Accumulates iron, usually in the spleen and liver, and the kidneys and pancreas.
In the human diet should be the foods that contain iron:
The Lack of iron in the blood, leads to a decrease in haemoglobin and development of such diseases as iron deficiency anemia.
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