What is the oxidation state of oxygen? Valency and oxidation state of oxygen

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What is the oxidation state of oxygen? Valency and oxidation state of oxygen
What is the oxidation state of oxygen? Valency and oxidation state of oxygen

We all breathe air, which mainly consists of nitrogen and oxygen molecules with a minor addition of other elements. Thus, oxygen is one of the most important chemical elements. In addition, its molecules exist in a huge variety of chemical compounds used in everyday life. A hundred pages are not enough to describe all the properties of this element, so we will limit ourselves to the main facts from the history, as well as the basic characteristics of the element - valence and oxidation state of oxygen, specific gravity, application, basic physical properties.

History of the discovery of a chemical element

The official date for the discovery of the chemical element "oxygen" is August 1, 1774. It was on this day that the British chemist J. Priestley completed his experiment on the decomposition of mercury oxide in a hermetically sealed vessel. At the end of the experiment, the scientist received a gas that supported combustion. However, this discovery went unnoticed even by the scientists themselves. Mr. Priestley thought that he had succeeded in isolating not a new element, butconstituent of air. Joseph Priestley shared his results with the famous French scientist and chemist Antoine Lavoisier, who was able to understand what the Englishman could not do. In 1775, Lavoisier was able to establish that the resulting "component of air" was in fact an independent chemical element, and he named it oxygen, which in Greek means "forming acids." Lavoisier then believed that oxygen is found in all acids. Subsequently, the formulas of acids that did not contain oxygen atoms were derived, but the name stuck.

Oxygen - structural features of the molecule

This chemical element is a colorless gas, odorless and tasteless. The chemical formula is O2. Chemists refer to ordinary diatomic oxygen as either "atmospheric oxygen" or "dioxygen".

what is the oxidation state of oxygen

A substance molecule consists of two bonded oxygen atoms. There is also a molecule consisting of three atoms - O3. This substance is called ozone, more details about it will be written below. A molecule with two atoms has an oxygen oxidation state of -2, since it has two unpaired electrons capable of forming a covalent bond. The energy that is released during the decomposition (dissociation) of an oxygen molecule into atoms is 493.57 kJ / mol. This is quite a big value.

Valence and oxidation state of oxygen

Under the valence of a chemical element, they mean its ability to attach a certain number of atoms to itselfanother chemical element. The valency of the oxygen atom is two. The valence of an oxygen molecule is also equal to two, since two atoms are connected to each other and have the ability to attach one more atom of another compound to their structure, that is, to form a covalent bond with it. For example, the water molecule H2O resulted from the formation of a covalent bond between one oxygen atom and two hydrogen atoms.

Oxygen is found in many of the known chemical compounds. There is even a separate type of chemical compounds - oxides. These are substances obtained by combining almost any chemical element with oxygen. The oxidation state of oxygen in oxides is -2. However, in some compounds, this indicator may be different. This will be discussed in more detail below.

Physical properties of oxygen

Ordinary diatomic oxygen is a gas that is colorless, odorless and tasteless. In its normal state, its density is 1.42897 kg/m3. The weight of 1 liter of a substance is slightly less than 1.5 grams, that is, in its pure form, oxygen is heavier than air. When heated, the molecule dissociates into atoms.

oxidation state of oxygen in peroxide

When the medium temperature drops to -189.2 оС oxygen changes its structure from gaseous to liquid. This is where boiling occurs. When the temperature decreases to -218, 35 оС, the structure changes from liquid to crystalline. At this temperature, oxygen has the form of bluish crystals.

At room temperature, oxygen is slightly soluble in water - 31 milliliters of oxygen per liter of it. Solubility with other substances: 220 ml per 1 liter of ethanol, 231 ml per 1 liter of acetone.

Chemical properties of oxygen

A whole Talmud can be written about the chemical properties of oxygen. The most important property of oxygen is oxidation. This substance is a very strong oxidizing agent. Oxygen is able to interact with almost all known elements from the periodic table. As a result of this interaction, oxides are formed, as mentioned earlier. The oxidation states of oxygen in compounds with other elements are basically -2. An example of such compounds is water (H2O), carbon dioxide (CO2), calcium oxide, lithium oxide, etc. But there is a certain category oxides, called peroxides or peroxides. Their feature is that in these compounds there is a peroxide group "-О-О-". This group reduces the oxidizing properties of O2, so the oxidation state of oxygen in peroxide is -1.

highest oxidation state of oxygen

In combination with active alkali metals, oxygen forms superoxides or superoxides. An example of such formations is:

  • potassium superoxide (KO2);
  • rubidium superoxide (RbO2).

Their feature is that the oxidation state of oxygen in superoxides is -1/2.

In combination with the most active chemical element - fluorine, fluorides are obtained. About them willdescribed below.

The highest oxidation state of oxygen in compounds

Depending on what substance oxygen interacts with, there are seven oxidation states of oxygen:

  1. -2 - in oxides and organic compounds.
  2. -1 - in peroxides.
  3. -1/2 - in superoxides.
  4. -1/3 - in inorganic ozonides (true for triatomic oxygen - ozone).
  5. +1/2 - in s alts of the oxygen cation.
  6. +1 – in oxygen monofluoride.
  7. +2 – in oxygen difluoride.

As you can see, the highest degree of oxygen oxidation is achieved in oxides and organic compounds, and in fluorides it even has a positive degree. Not all types of interactions can be done naturally. Some compounds require special conditions to form, for example: high pressure, high temperature, exposure to rare compounds that are almost never found in nature. Consider the main compounds of oxygen with other chemical elements: oxides, peroxides and fluorides.

Classification of oxides by acid-base properties

There are four types of oxides:

  • basic;
  • acid;
  • neutral;
  • amphoteric.

The oxidation states of oxygen in compounds of these species are -2.

  • Basic oxides are compounds with metals with low oxidation states. Usually, when reacted with acids, the corresponding s alt and water are obtained.
  • Acid oxides - oxides of non-metals with a high degree of oxidation. When added towater forms acid.
  • Neutral oxides are compounds that do not react with either acids or bases.
  • Amphoteric oxides are compounds with metals that have a low electronegativity value. They, depending on the circumstances, exhibit the properties of both acidic and basic oxides.

Peroxides, the oxidation state of oxygen in hydrogen peroxide and other compounds

Peroxides are compounds of oxygen with alkali metals. They are obtained by burning these metals in oxygen. Peroxides of organic compounds are extremely explosive. They can also be obtained by absorption by oxygen oxides. Examples of peroxides:

  • hydrogen peroxide (H2O2);
  • barium peroxide (BaO2);
  • sodium peroxide (Na2O2).

All of them are united by the fact that they contain an oxygen group -O-O-. As a result, the oxidation state of oxygen in peroxides is -1.

oxidation state of oxygen

One of the most famous compounds with the -O-O- group is hydrogen peroxide. Under normal conditions, this compound is a pale blue liquid. According to its chemical properties, hydrogen peroxide is closer to a weak acid. Since the -O-O- bond in the compound is weakly stable, even at room temperature, a hydrogen peroxide solution can be decomposed into water and oxygen. It is the strongest oxidizing agent, however, when interacting with stronger oxidizing propertiesthe reducing agent possesses just hydrogen peroxide. The oxidation state of oxygen in hydrogen peroxide, as in other peroxides, is -1.

Other types of peroxides are:

  • superoxides (superoxides in which oxygen has an oxidation of -1/2);
  • inorganic ozonides (extremely unstable compounds having an ozone anion in their structure);
  • organic ozonides (compounds having an -O-O-O- bond in their structure).

Fluorides, oxidation state of oxygen in OF2

Fluorine is the most active element of all currently known. Therefore, when oxygen reacts with fluorine, not oxides are obtained, but fluorides. They are so named because in this compound, not oxygen, but fluorine is an oxidizing agent. Fluorides cannot be obtained naturally. They are only synthesized by extracting by association of fluorine with an aqueous solution of KOH. Oxygen fluorides are divided into:

  • oxygen difluoride (OF2);
  • oxygen monofluoride (O2F2).

Let's take a closer look at each of the compounds. Oxygen difluoride in its structure is a colorless gas with a pronounced unpleasant odor. On cooling, it condenses to a yellowish liquid. In the liquid state, it does not mix well with water, but it does well with air, fluorine and ozone. According to its chemical properties, oxygen difluoride is a very strong oxidizing agent. The oxidation state of oxygen in OF2 is +1, that is, in this compound, fluorine is an oxidizing agent, and oxygen is a reducing agent. OF2 very toxic, in terms of toxicityexceeds pure fluorine and approaches phosgene. The main use of this compound is as an oxidizer for rocket fuel, since oxygen difluoride is not explosive.

Oxygen monofluoride is normally a yellowish solid. On melting it forms a red liquid. It is a powerful oxidizing agent, when interacting with organic compounds it is extremely explosive. In this compound, oxygen exhibits oxidation states equal to +2, that is, in this fluorine compound, oxygen acts as a reducing agent, and fluorine acts as an oxidizing agent.

Ozone and its compounds

Ozone is a molecule that has three oxygen atoms bonded to each other. In its normal state, it is a blue gas. On cooling, it forms a deep blue liquid, close to indigo. In the solid state, it is dark blue crystals. Ozone has a pungent odor, in nature it can be felt in the air after a heavy thunderstorm.

oxidation state of oxygen in ozone

Ozone, like ordinary oxygen, is a very strong oxidizing agent. By chemical properties, it approaches strong acids. When exposed to oxides, ozone increases their oxidation state with the release of oxygen. But at the same time, the degree of oxidation of oxygen decreases. In ozone, chemical bonds are not as strong as in O2, therefore, under normal conditions, without effort, it can decompose into oxygen with the release of heat energy. With an increase in the temperature of the impact on the ozone molecule and with a decrease in pressure, the processdecay into diatomic oxygen with the release of heat is accelerated. At the same time, if there is a high content of ozone in space, then this process may be accompanied by an explosion.

Since ozone is a very strong oxidizing agent and in almost all processes with its participation a large amount of O2 is released, ozone is an extremely toxic substance. However, in the upper atmosphere, the ozone layer acts as a reflector from the ultraviolet radiation of the sun's rays.

Ozone is used to create organic and inorganic ozonides using laboratory tools. These are very unstable substances in their structure, so their creation in natural conditions is impossible. Ozonides are stored only at low temperatures, as at ordinary temperatures they are extremely explosive and toxic.

Use of oxygen and its compounds in industry

Due to the fact that at one time scientists learned what degree of oxidation oxygen has when interacting with other elements, it and its compounds are widely used in industry. Especially after the invention of turboexpanders in the middle of the twentieth century - units capable of converting the potential energy of oxygen into mechanical energy.

maximum oxidation state of oxygen

Since oxygen is an extremely flammable substance, it is used in all industries where the use of fire and heat is necessary. When cutting and welding metals, compressed oxygen cylinders are also used to strengthen the flame welding apparatus. Widethe use of oxygen in the steel industry, where compressed O2 is used to maintain high temperatures in blast furnaces. The maximum oxidation state of oxygen is -2. This characteristic of it is actively used for the manufacture of oxides for the purpose of their further combustion and release of thermal energy. Liquid oxygen, ozone and other compounds containing large amounts of O2, are used as rocket fuel oxidizers. Some organic compounds oxidized with oxygen are used as explosives.

oxygen exhibits oxidation states

In the chemical industry, oxygen is used as an oxidizing agent for hydrocarbons in acidic compounds such as alcohols, acids, etc. In medicine, it is used under reduced pressure to treat patients with lung problems, to maintain the body's vital functions. In agriculture, small doses of pure oxygen are used to breed fish in ponds, to increase the proportion of cattle, etc.

Oxygen is a powerful oxidizing agent, without which existence is impossible

A lot has been written above about which oxygen shows oxidation states when it reacts with various compounds and elements, what types of oxygen compounds exist, which types are life-threatening and which are not. One thing may remain incomprehensible - how, with all its toxicity and high level of oxidation, is oxygen one of the elements without which life on Earth is impossible? The fact is that our planet is a very balanced organism,which has adapted precisely to those substances that are contained in the atmospheric layer. It participates in the cycle, which looks like this: a person and all other animals consume oxygen and produce carbon dioxide, and plants overwhelmingly consume carbon dioxide and produce oxygen. Everything in the world is interconnected, and the loss of one link in this chain can lead to a break in the entire chain. We should not forget about this and protect life on the planet as a whole, and not just its individual representatives.

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