Chlorine: a characteristic of chemical and physical properties
No matter how negatively we treat public restrooms, nature dictates its own rules, and we have to attend them. In addition to natural (for this place) odors, another familiar fragrance is bleach used to disinfect the room. It received its name because of the main active ingredient in it - Cl. Let us know about this chemical element and its properties, as well as give a characteristic of chlorine on the position in the periodic system.
How was this item opened
The first chlorine-containing compound (HCl) was synthesized in 1772 by the British priest Joseph Priestley.
After 2 years, his Swedish counterpart, Karl Scheele, was able to describe a method for separating Cl using a reaction between hydrochloric acid and manganese dioxide. However, this chemist did not understand that a new chemical element was synthesized as a result.
Almost 40 years it took scientists to learn how to extract chlorine in practice.This was first done by the British Humphry Davy in 1811. At the same time, he used a different reaction than his predecessors theorists. Davy using electrolysis decomposed into components of NaCl (known to most as kitchen salt).
Having studied the substance, the British chemist realized that it is elementary. After this discovery, Davy not only called it chlorine (chlorine), but was able to characterize chlorine, although it was very primitive.
Chlorine has turned into chlorine (chlore) thanks to Joseph Gay-Lussac and as such exists in French, German, Russian, Belarusian, Ukrainian, Czech, Bulgarian and some other languages today. In English to this day the name "chlorine" is used, and in Italian and Spanish "chloro".
The element in question was described in more detail by Jens Berzelius in 1826. It was he who was able to determine its atomic mass.
What is chlorine (Cl)
Having considered the history of the discovery of this chemical element, it is worth knowing more about it.
The name chlorine was derived from the Greek word χλωρός ("green"). It was given because of the yellowish-greenish color of the substance
Chlorine exists independently as a diatomic gas Cl2,however, in this form in nature, it practically does not occur. More often it appears in various connections.
In addition to the distinctive shade, chlorine has a sweet-pungent odor. It is a very poisonous substance, therefore, if it is released into the air and inhaled by a human or animal, it can lead to their death within a few minutes (depends on the concentration of Cl).
Since chlorine is almost 2.5 times heavier than air, it will always be below it, that is, near the ground itself. For this reason, if Cl is suspected, one should climb as high as possible, since there will be a lower concentration of this gas.
Also, unlike some other toxic substances, chlorine-containing materials have a characteristic color, which may allow them to visually identify and take action. Most standard gas masks help protect the respiratory organs and mucous membranes from Cl. However, for complete safety, it is necessary to take more serious measures, including the neutralization of toxic substances.
It is worth noting that it was with the use of chlorine by the Germans as a poison gas in 1915.began its history of chemical weapons. As a result of the use of nearly 200 tons of substance, 15,000 people were poisoned in a few minutes. A third of them died almost instantly, a third received permanent damage, and only 5 thousand managed to escape.
Why is it that such a dangerous substance has not yet been banned and millions of tons are produced annually? It's all about its special properties, and to understand them, it is worth considering the characteristics of chlorine. The easiest way to do this is with the help of the periodic table.
Characteristics of chlorine in the periodic system
- Chlorine is a simple substance.
- It has the seventeenth number in order (possesses 17 protons in the atomic nucleus).
- Located in the third period and third row.
- Chlorine is located in the VII group (subgroup "a").
- The atomic mass of Cl is 35.453 a. eat.
- A molecule of simple chlorine substance consists of two atoms: Cl2↑.
- Chlorine is a non-metal and goes to the halogen group. By the way, in the past they wanted to call this element this term. But later it became the general name of the 17th group. In addition to chlorine, halogens include fluorine, bromine, iodine, astatine, and recently discovered tennesin.
- Electronic chlorine configuration - 3s23p5.
- The Cl atom at the valence level contains one unpaired electron. Due to this, with valence І it is very stable (NaCl, Cl2↑).
- This element at the atomic level has an unoccupied d-sublevel orbital. Due to this, chlorine is able to exhibit various degrees of oxidation (from -1 to +7).
Chlorine as halogen
In addition to extreme toxicity and caustic odor (characteristic of all members of this group), Cl is perfectly soluble in water. Practical confirmation of this is the addition of chlorine-containing detergents to swimming pool water.
Upon contact with moist air, the substance in question begins to smoke.
Cl properties as non-metal
Considering the chemical characteristics of chlorine, you should pay attention to its non-metallic properties.
It has the ability to form compounds with almost all metals and non-metals. As an example, the reaction with iron atoms: 2Fe + 3Cl2↑ → 2FeCl3.
Often, catalysts must be used for the reactions. H can play this role.2ABOUT.
Often, reactions with Cl are endothermic in nature (they absorb heat).
It should be noted that in the crystalline form (in the form of powder) chlorine interacts with metals only when heated to high temperatures.
Reacting with other non-metals (except O2↑, N, F, C and inert gases), Cl forms compounds - chlorides.
When reacting with O2↑extremely unstable and decay-prone oxides are formed. In them, the degree of Cl oxidation can manifest itself from +1 to +7.
When interacting with F, fluorides are formed. The degree of oxidation may vary.
Chlorine: a characteristic of a substance in terms of its physical properties
In addition to chemical properties, the element in question also has physical ones.
- As mentioned above, a gaseous state (under normal conditions) is natural for a given substance. However, when the temperature changes, it is able to remain both in the liquid and in the solid state.
- Color: yellow-green.
- The density of Cl under standard conditions is 3.214 g / l.
- When boiling (liquid) density changes and becomes 1,537 g / cm3.
- Being in a solid state of aggregation, Cl gains density - 1.9 g / cm3.
- The atomic radius is 0.073 nm.
- Chlorine boils at t -34 degrees Celsius.
- The melting point is −100 degrees Celsius.
- The specific volume of chlorine - 1,745 x 10-3l / g
The effect of temperature on the state of aggregation Cl
Having considered the physical characteristics of the element of chlorine, we understand that it is capable of passing into different state of aggregation. It all depends on the temperature.
In the normal state, Cl is a gas with high corrosive properties. However, it can easily liquefy. This is influenced by temperature and pressure. For example, if it is equal to 8 atmospheres, and temperature - +20 degrees C, Cl2↑-acid yellow liquid. This aggregative state, it is able to maintain up to +143 degrees, if the pressure also continues to rise.
Upon reaching-32 ° С state of chlorine ceases to depend on pressure, and it continues to remain liquid.
The crystallization of the substance (solid state) occurs at -101 degrees.
Where does Cl exist in nature?
Having considered the general characteristics of chlorine, it is worth knowing where in nature such an uneasy element can occur.
Because of its high reactivity, it almost never occurs in its pure form (therefore, at the beginning of the study, scientists of this element took years to learn how to synthesize it). Usually Cl is found in compounds in various minerals: halite, sylvin, cainite, bischofite, etc.
Most of all, it is contained in salts extracted from sea or ocean water.
Effect on the body
When considering the characteristics of chlorine, it has been said many times that it is extremely toxic.At the same time, the atoms of a substance are contained not only in minerals, but practically in all organisms, ranging from plants to humans.
Due to the special properties, Cl ions penetrate the cell membranes better than others (therefore, more than 80% of all chlorine in the human body is in the intercellular space).
Together with K, Cl is responsible for the regulation of water-salt balance and, as a result, for osmotic equality.
Despite such an important role in the body, in its pure form Cl2↑ kills all living things - from cells to whole organisms. However, in controlled doses and with short-term exposure, he does not have time to cause damage.
A vivid example of the last statement is any pool. As you know, water in such institutions is disinfected with Cl. At the same time, if a person rarely visits such an institution (once a week or a month) - it is unlikely that he will suffer from the presence of this substance in the water. However, employees of such institutions, especially those who spend most of the day in the water (rescuers, instructors) often suffer from skin diseases or have weakened immunity.
In connection with all this, it is imperative to take a shower after visiting the pools - in order to wash off possible chlorine residues from skin and hair.
Use of Cl by man
Bearing in mind the characteristic of chlorine that it is a “capricious” element (when it comes to interaction with other substances), it will be interesting to learn that it is used quite often in industry.
First of all, it is used to disinfect many substances.
Cl is also used in the manufacture of certain types of pesticides, which helps to save the crop from pests.
The ability of this substance to interact with almost all elements of the periodic table (characteristic of chlorine as a non-metal) helps with its help to extract some types of metals (Ti, Ta and Nb), as well as lime and hydrochloric acid.
In addition to all of the above, Cl is used in the production of industrial substances (polyvinyl chloride) and medical drugs (chlorhexidine).
It is worth mentioning that today found a more effective and safe disinfectant - ozone (O3↑). However, its production is more expensive than chlorine, and this gas is even more unstable than chlorine (a brief description of the physical properties in 6-7 p.). Therefore, only a few can afford to use ozonation instead of chlorination.
How is chlorine produced
Today, there are many ways to synthesize this substance. All of them are divided into two categories:
In the first case, Cl is obtained due to a chemical reaction. However, in practice they are very costly and inefficient.
Therefore, in the industry prefer electrochemical methods (electrolysis). There are three of them: diaphragm, membrane and mercury electrolysis.