Allotropic modifications of oxygen: comparative characteristic and value

Atoms of one kind can be part of differentsubstances. For an element designated by the symbol "O" (from the Latin name Oxygenium), two common simple substances are known in nature. The formula of one of them is O_2, the second - O_3. These are allotropic modifications of oxygen (allotropes). There are other compounds that are less stable (O₄ and O₈). To understand the difference between these forms will help to compare molecules and properties of substances.

What are allotropic modifications?

Many chemical elements can exist intwo, three or more forms. Each of these modifications is formed by atoms of the same species. The scientist J. Berzellius in 1841 was the first to call such a phenomenon an allotropy. The open regularity was originally used only to characterize the substances of the molecular structure. For example, two allotropic modifications of oxygen are known, the atoms of which form molecules. Later, researchers established that the modifications may be among the crystals. According to modern concepts, allotropy is one of the cases of polymorphism. Differences between forms are caused by mechanisms of formation of a chemical bond in molecules and crystals. This feature is manifested mainly elements of groups 13-16 of the periodic table.

How does a different combination of atoms affect the properties of matter?

Allotropic modifications of oxygen and ozoneare formed by the atoms of the element with the ordinal number 8 and the same number of electrons. But they differ in structure, which caused a significant discrepancy in the properties.

Comparison of oxygen and ozone

Symptoms	Oxygen	Ozone
Composition of the molecule	2 oxygen atoms	3 oxygen atoms
Structure
Aggregate state and color	Colorless transparent gas or pale blue liquid	Blue gas, blue liquid, dark purple solid
Smell	Absent	Sharp, reminiscent of thunder, freshly mown hay
Melting point (° C)	-219	-193
Boiling Point (° C)	-183	-112
Density (g / l)	1,4	2,1
Solubility in water	Slightly soluble	Better than oxygen
Chemical activity	Under normal conditions, stable	It is easy to decompose with the formation of oxygen

Conclusions from the results of the comparison: allotropic modifications of oxygen do not differ in qualitative composition. The structure of the molecule is reflected in the physical and chemical properties of the substances.

Is the same amount of oxygen and ozone in nature?

A substance whose formula O₂, occurs in the atmosphere, hydrosphere, terrestrialbark and living organisms. About 20% of the atmosphere is formed by diatomic oxygen molecules. In the stratosphere at an altitude of about 12-50 km from the earth's surface there is a layer called "ozone screen". Its composition reflects the formula O₃. Ozone protects our planet by absorbingdangerous rays of the red and ultraviolet spectrum of the Sun. The concentration of the substance is constantly changing, and its average value is low - 0.001%. Thus, O₂ and O₃ - allotropic modifications of oxygen, which have significant differences in their distribution in nature.

How to get oxygen and ozone?

Molecular oxygen is the most important simplematter on Earth. It forms in the green parts of plants in the light during photosynthesis. With electric discharges of natural or artificial origin, a diatomic oxygen molecule breaks up. The temperature at which the process begins is about 2000 ° C. Some of the radicals that have arisen are reunited, forming oxygen. Some active particles react with diatomic oxygen molecules. In this reaction, ozone is produced, which also reacts with free radicals of oxygen. In this case, diatomic molecules arise. Reversibility of reactions leads to the fact that the concentration of atmospheric ozone is constantly changing. In the stratosphere, the formation of a layer consisting of O₃, is associated with ultraviolet radiation of the sun. Without this protective shield, dangerous rays could reach the surface of the Earth and destroy all forms of life.

Allotropic modifications of oxygen and sulfur

The chemical elements O (Oxygenium) and S (Sulfur)are located in the same group of the periodic table, they are characterized by the formation of allotropic forms. Of molecules with different numbers of sulfur atoms (2, 4, 6, 8) under normal conditions, the most stable is S8, resembling a crown in shape. The rhombic and monoclinic sulfur are constructed from such 8-atom molecules.

At a temperature of 119 ° C, the monoclinic form of yellowcolor forms a brown viscous mass - plastic modification. The study of allotropic modifications of sulfur and oxygen is of great importance in theoretical chemistry and practical activity.

On an industrial scale,oxidizing properties of different forms. Ozone is used for disinfection of air and water. But at concentrations above 0.16 mg / m3, this gas is dangerous for humans and animals. Molecular oxygen is essential for breathing, it is used in industry and medicine. Allotropes of carbon (diamond, graphite), phosphorus (white, red) and other chemical elements play an important role in economic activity.