In nature, chlorine occurs in the gaseous state and only in the form of compounds with other gases. Under conditions close to normal, it is a greenish, poisonous, caustic gas. It has more weight than air. Has a sweet smell. The chlorine molecule contains two atoms. It does not burn at rest, but at high temperatures it interacts with hydrogen, after which an explosion is possible. As a result, phosgene gas is released. Very poisonous. So, even at a low concentration in the air (0.001 mg per 1 dm3) can cause death. The main characteristic of the non-metal chlorine is that it is heavier than air, therefore, it will always be near the floor in the form of a yellowish-green haze.
Historical facts
For the first time in practice, this substance was obtained by K. Schelee in 1774 by combining hydrochloric acid and pyrolusite. However, only in 1810, P. Davy was able to characterize chlorine and establish that ita separate chemical element.
It is worth noting that in 1772 Joseph Priestley was able to obtain hydrogen chloride - a compound of chlorine with hydrogen, but the chemist could not separate these two elements.
Chemical characterization of chlorine
Chlorine is a chemical element of the main subgroup of group VII of the periodic table. It is in the third period and has atomic number 17 (17 protons in the atomic nucleus). Reactive nonmetal. Designated by letters Cl.
Is a typical representative of halogens. These are gases that do not have a color, but have a sharp pungent odor. Usually toxic. All halogens are highly soluble in water. They begin to smoke when exposed to moist air.
External electronic configuration of the atom Cl 3s2Зр5. Therefore, in compounds, the chemical element exhibits oxidation levels of -1, +1, +3, +4, +5, +6 and +7. The covalent radius of the atom is 0.96 Å, the ionic radius of Cl is 1.83 Å, the affinity of the atom to the electron is 3.65 eV, the ionization level is 12.87 eV.
As mentioned above, chlorine is a fairly active non-metal, which allows you to create compounds with almost any metal (in some cases, by heating or using moisture, displacing bromine) and non-metals. In powder form, it reacts with metals only when exposed to high temperatures.
Maximum combustion temperature - 2250 °C. With oxygen, it can form oxides, hypochlorites, chlorites and chlorates. All compounds containing oxygen become explosive when interacting with oxidizingsubstances. It is worth noting that chlorine oxides can explode randomly, while chlorates explode only when exposed to any initiators.
Characterization of chlorine by position in the Periodic Table:
• simple substance;
• element of the seventeenth group of the periodic table;
• third period of the third row;
• seventh group of the main subgroup;
• atomic number 17;
• symbol Cl;
• reactive non-metal;
• is in the halogen group;
• under near normal conditions, it is a poisonous gas yellowish-green in color with a pungent odor;
• chlorine molecule has 2 atoms (formula Cl2).
Physical properties of chlorine:
• Boiling point: -34.04 °С;
• Melting point: -101.5 °С;
• Gaseous density - 3.214 g/l;
• density of liquid chlorine (during the boiling period) – 1.537 g/cm3;
• density of solid chlorine – 1.9 g/cm 3;
• specific volume – 1.745 x 10-3 l/year.
Chlorine: characteristics of temperature changes
In the gaseous state, it tends to liquefy easily. At a pressure of 8 atmospheres and a temperature of 20 ° C, it looks like a greenish-yellow liquid. It has very high corrosion properties. As practice shows, this chemical element can maintain a liquid state up to a critical temperature (143 ° C), subject to an increase in pressure.
If it is cooled down to -32 °C,it will change its state of aggregation to liquid, regardless of atmospheric pressure. With a further decrease in temperature, crystallization occurs (at -101 ° C).
Chlorine in nature
The earth's crust contains only 0.017% chlorine. The bulk is in volcanic gases. As indicated above, the substance has a high chemical activity, as a result of which it occurs in nature in compounds with other elements. However, many minerals contain chlorine. The characteristic of the element allows the formation of about a hundred different minerals. As a rule, these are metal chlorides.
Also, a large amount of it is in the oceans - almost 2%. This is due to the fact that chlorides are very actively dissolved and carried by rivers and seas. The reverse process is also possible. Chlorine is washed back to the shore, and then the wind carries it around. That is why its highest concentration is observed in coastal zones. In the arid regions of the planet, the gas we are considering is formed by the evaporation of water, as a result of which s alt marshes appear. About 100 million tons of this substance are mined annually in the world. Which, however, is not surprising, because there are many deposits containing chlorine. Its characteristics, however, largely depend on its geographical location.
Methods for obtaining chlorine
Today, there are a number of methods for obtaining chlorine, of which the following are the most common:
1. diaphragm. It is the simplest and least expensive. hydrochloricthe solution in diaphragm electrolysis enters the anode space. Further on the steel cathode grid flows into the diaphragm. It contains a small amount of polymer fibers. An important feature of this device is counterflow. It is directed from the anode space to the cathode space, which makes it possible to obtain chlorine and lye separately.
2. Membrane. The most energy efficient, but difficult to implement in an organization. Similar to diaphragm. The difference is that the anode and cathode spaces are completely separated by a membrane. Therefore, the output is two separate streams.
It is worth noting that the characteristic of chem. element (chlorine) obtained by these methods will be different. The membrane method is considered to be more "clean".
3. Mercury method with liquid cathode. Compared to other technologies, this option allows you to get the purest chlorine.
Principal diagram of the installation consists of an electrolyzer and interconnected pump and amalgam decomposer. The mercury pumped by the pump together with a solution of common s alt serves as the cathode, and carbon or graphite electrodes serve as the anode. The principle of operation of the installation is as follows: chlorine is released from the electrolyte, which is removed from the electrolyzer together with the anolyte. Impurities and chlorine residues are removed from the latter, saturated with halite and returned to electrolysis again.
Industrial safety requirements and production unprofitability led to the replacement of the liquid cathode with a solid one.
The use of chlorine in industrialpurposes
The properties of chlorine allow it to be actively used in industry. With the help of this chemical element, various organochlorine compounds (vinyl chloride, chloro-rubber, etc.), drugs, and disinfectants are obtained. But the biggest niche occupied by the industry is the production of hydrochloric acid and lime.
Methods for purifying drinking water are widely used. Today, they are trying to move away from this method, replacing it with ozonation, since the substance we are considering negatively affects the human body, besides, chlorinated water destroys pipelines. This is due to the fact that in the free state Cl adversely affects pipes made from polyolefins. However, most countries prefer the chlorination method.
Also, chlorine is used in metallurgy. With its help, a number of rare metals (niobium, tantalum, titanium) are obtained. In the chemical industry, various organochlorine compounds are actively used for weed control and for other agricultural purposes, the element is also used as a bleach.
Due to its chemical structure, chlorine destroys most organic and inorganic dyes. This is achieved by completely discoloring them. Such a result is possible only if water is present, because the bleaching process occurs due to atomic oxygen, which is formed after the breakdown of chlorine: Cl2 + H2O → HCl + HClO → 2HCl + O. This method has been used by a couplecenturies ago and is still popular today.
The use of this substance is very popular for the production of organochlorine insecticides. These agricultural preparations kill harmful organisms, leaving plants intact. A significant part of all chlorine mined on the planet goes to agricultural needs.
It is also used in the production of plastic compounds and rubber. With their help, wire insulation, stationery, equipment, shells of household appliances, etc. are made. There is an opinion that rubbers obtained in this way harm a person, but this is not confirmed by science.
It is worth noting that chlorine (the characteristics of the substance were disclosed in detail by us earlier) and its derivatives, such as mustard gas and phosgene, are also used for military purposes to obtain chemical warfare agents.
Chlorine as a bright representative of non-metals
Non-metals are simple substances that include gases and liquids. In most cases, they conduct electric current worse than metals, and have significant differences in physical and mechanical characteristics. With the help of a high level of ionization, they are able to form covalent chemical compounds. Below, a characteristic of a non-metal will be given using the example of chlorine.
As mentioned above, this chemical element is a gas. Under normal conditions, it completely lacks properties similar to those of metals. Without outside help, it cannot interact with oxygen, nitrogen, carbon, etc.exhibits oxidizing properties in bonds with simple substances and some complex ones. Refers to halogens, which is clearly reflected in its chemical characteristics. In compounds with other representatives of halogens (bromine, astatine, iodine), it displaces them. In the gaseous state, chlorine (its characteristic is a direct confirmation of this) dissolves well. It is an excellent disinfectant. It only kills living organisms, making it indispensable in agriculture and medicine.
Use as a poisonous substance
The characteristic of the chlorine atom allows it to be used as a poisonous agent. For the first time, gas was used by Germany on April 22, 1915, during the First World War, as a result of which about 15 thousand people died. At the moment, it is not used as a poisonous substance.
Let's give a brief description of the chemical element as a suffocating agent. Affects the human body through suffocation. First, it irritates the upper respiratory tract and mucous membranes of the eyes. A strong cough begins with attacks of suffocation. Further, penetrating into the lungs, the gas corrodes the lung tissue, which leads to edema. Important! Chlorine is a fast acting substance.
Depending on the concentration in the air, the symptoms are different. With a low content in a person, redness of the mucous membrane of the eyes, slight shortness of breath is observed. The content in the atmosphere of 1.5-2 g/m3 causes heaviness and thrills in the chest, sharp pain in the upper respiratory tract. Also, the condition may be accompanied by severe lacrimation. After 10-15 minutes of being in the roomwith such a concentration of chlorine, a severe burn of the lungs and death occurs. At higher concentrations, death is possible within a minute from paralysis of the upper respiratory tract.
When working with this substance, it is recommended to use overalls, gas masks, gloves.
Chlorine in the life of organisms and plants
Chlorine is part of almost all living organisms. The peculiarity is that it is present not in its pure form, but in the form of compounds.
In organisms of animals and humans, chloride ions maintain osmotic equality. This is due to the fact that they have the most suitable radius for penetration into membrane cells. Along with potassium ions, Cl regulates the water-s alt balance. In the intestine, chloride ions create a favorable environment for the action of proteolytic enzymes of gastric juice. Chlorine channels are provided in many cells of our body. Through them, intercellular fluid exchange occurs and the pH of the cell is maintained. About 85% of the total volume of this element in the body resides in the intercellular space. It is excreted from the body through the urethra. Produced by the female body during breastfeeding.
At this stage of development, it is difficult to unequivocally say which diseases are provoked by chlorine and its compounds. This is due to the lack of research in this area.
Also, chloride ions are present in plant cells. He actively takes part in the energy exchange. Without this element, the process of photosynthesis is impossible. With his helpthe roots actively absorb the necessary substances. But a high concentration of chlorine in plants can have a detrimental effect (slowing down the process of photosynthesis, stopping development and growth).
However, there are such representatives of the flora that could "make friends" or at least get along with this element. The characteristic of a non-metal (chlorine) contains such an item as the ability of a substance to oxidize soils. In the process of evolution, the plants mentioned above, called halophytes, occupied empty s alt marshes, which were empty due to an overabundance of this element. They absorb chloride ions, and then get rid of them with the help of leaf fall.
Transportation and storage of chlorine
There are several ways to move and store chlorine. The characteristic of the element implies the need for special high-pressure cylinders. Such containers have an identification marking - a vertical green line. Cylinders must be thoroughly rinsed monthly. With prolonged storage of chlorine, a very explosive precipitate is formed in them - nitrogen trichloride. Spontaneous ignition and explosion is possible if all safety rules are not observed.
Studying chlorine
Future chemists should know the characteristics of chlorine. According to the plan, 9th graders can even make laboratory experiments with this substance based on basic knowledge of the discipline. Naturally, the teacher is obliged to conduct a safety briefing.
The order of work is as follows: you need to take a flask withchlorine and pour small metal shavings into it. In flight, the chips will flare up with bright bright sparks and at the same time light white smoke SbCl3 is formed. When tin foil is immersed in a vessel with chlorine, it will also spontaneously ignite, and fiery snowflakes will slowly fall to the bottom of the flask. During this reaction, a smoky liquid is formed - SnCl4. When iron shavings are placed in the vessel, red “drops” form and red smoke appears FeCl3.
Along with practical work, theory is repeated. In particular, such a question as the characterization of chlorine by position in the periodic system (described at the beginning of the article).
As a result of the experiments, it turns out that the element actively reacts to organic compounds. If you place cotton wool soaked in turpentine in a jar of chlorine, it will instantly ignite, and soot will fall sharply from the flask. Sodium effectively smolders with a yellowish flame, and s alt crystals appear on the walls of chemical dishes. Students will be interested to know that, while still a young chemist, N. N. Semenov (later Nobel Prize winner), after conducting such an experiment, collected s alt from the walls of the flask and, sprinkling bread with it, ate it. Chemistry turned out to be right and did not let the scientist down. As a result of the experiment carried out by the chemist, ordinary table s alt really turned out!
