Atoms of the same type can be part of different substances. For the element denoted by the symbol "O" (from the Latin name Oxygenium), two simple substances common in nature are known. The formula of one of them is O2, the second is O3. These are allotropic modifications of oxygen (allotropes). There are other compounds that are less stable (O4 and O8). Comparison of molecules and properties of substances will help to understand the difference between these forms.
What are allotropic modifications?
Many chemical elements can exist in two, three or more forms. Each of these modifications is formed by atoms of the same type. The scientist J. Berzellius in 1841 was the first to call such a phenomenon allotropy. The open regularity was originally used only to characterize substances of a molecular structure. For example, two allotropic modifications of oxygen are known, the atoms of which form molecules. Later, the researchers found that modifications can be among the crystals. According to modern concepts, allotropy is one of the cases of polymorphism. Differences between forms are caused by mechanismsformation of a chemical bond in molecules and crystals. This feature is mainly manifested by elements of groups 13-16 of the periodic table.
How do different combinations of atoms affect the properties of matter?
Allotropic modifications of oxygen and ozone are formed by atoms of the element with the atomic number 8 and the same number of electrons. But they differ in structure, which led to a significant discrepancy in properties.
| Signs | Oxygen | Ozone |
| Composition of the molecule | 2 oxygen atoms | 3 oxygen atoms |
| Building |
|
|
| Aggregate state and color | Colorless transparent gas or pale blue liquid | Blue gas, blue liquid, dark purple solid |
| Smell | Missing | Sharp, reminiscent of a thunderstorm, freshly cut hay |
| Melting point (°C) | -219 | -193 |
| Boiling point (°C) | -183 | -112 |
|
Density (g/l) |
1, 4 | 2, 1 |
| Water solubility | Slightly dissolves | Better than oxygen |
| Reactivity | Under normal conditionsstable | Easily decomposes to form oxygen |
Conclusions based on the results of comparison: allotropic modifications of oxygen do not differ in their qualitative composition. The structure of a molecule is reflected in the physical and chemical properties of substances.
Are the amounts of oxygen and ozone the same in nature?
Substance whose formula is O2, found in the atmosphere, hydrosphere, earth's crust 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 the "ozone screen". Its composition is reflected by the formula O3. Ozone protects our planet by intensely absorbing the dangerous rays of the red and ultraviolet spectrum of the sun. The concentration of a substance is constantly changing, and its average value is low - 0.001%. Thus, O2 and O3 are allotropic oxygen modifications that have significant differences in distribution in nature.
How to get oxygen and ozone?
Molecular oxygen is the most important simple substance on Earth. It is formed in the green parts of plants in the light during photosynthesis. With electrical discharges of natural or artificial origin, the diatomic oxygen molecule decomposes. The temperature at which the process starts is about 2000 °C. Some of the resulting radicals combine again, forming oxygen. Some active particles react with diatomic moleculesoxygen. This reaction produces ozone, which also reacts with oxygen free radicals. This creates diatomic molecules. The 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 molecules is associated with ultraviolet radiation from the Sun. Without this protective shield, dangerous rays could reach the surface of the Earth and destroy all life forms.
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 the molecules with different numbers of sulfur atoms (2, 4, 6, 8), under normal conditions, the most stable is S8, resembling a crown in shape. Rhombic and monoclinic sulfur are built from such 8-atom molecules.
At a temperature of 119 °C, the yellow monoclinic form forms a brown viscous mass - a plastic modification. The study of allotropic modifications of sulfur and oxygen is of great importance in theoretical chemistry and practical activities.
In industrial scale, the oxidizing properties of various forms are used. Ozone is used to disinfect 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 and is used in industry and medicine. Carbon allotropes play an important role in economic activity.(diamond, graphite), phosphorus (white, red) and other chemical elements.
