atoms of one species may be part of different substances.For an element, denoted by the symbol «O» (from Lat. Names Oxygenium), two widely known in the nature of simple substances.The formula of one of them - O2, the second - O3.This allotropic modification of oxygen (allotropes).There are other compounds are less stable (O4, and O8).Understand the difference between these forms will help the comparison of molecules and properties of substances.
What allotropic modification?
Many chemical elements may exist in two, three or more ways.Each of these modifications is formed by atoms of one species.Scientist J. Bertsellius in 1841 first described the phenomenon allotropism.Open law initially applied only to characterize the molecular structure of substances.For example, two known allotropic modification of oxygen atoms which form molecules.Later, researchers found that modifications may be among the crystals.According to modern concepts, allotropy is one of the cases of polymorphism.The differences between the forms caused by the mechanisms of the formation of chemical bonds in molecules and crystals.This is particularly evident in the basic elements 13-16 of the Periodic Table.
How different combination of atoms affects the properties of matter?
allotropic modification of oxygen and ozone are formed by atoms of the element with atomic number 8 and the same number of electrons.But they are different in structure, which resulted in a significant difference in the properties.
| Signs | Oxygen | Ozone |
| the molecule | 2 oxygen atoms | 3 oxygen atoms |
| structure |
| |
| Appearance andcolor | colorless transparent gas or pale blue liquid | Blue gas, liquid, blue, dark purple solid |
| Smell | No | sharp, reminiscent of a thunderstorm, mown hay |
| Melting point (° C.) | -219 | -193 |
| Boiling point (° C.) | -183 | -112 |
| density (g / l) | 14 | 2,1 |
| Solubility in water | Not soluble | Better than oxygen |
| Reactivity | Under normal conditions stable | easy decomposes to form oxygen |
Findings of comparison allotropic modification of oxygen do not differ in qualitative composition.The structure of the molecules affects the physical and chemical properties of substances.
Are the amount of oxygen and ozone in nature?
substance whose formula O2, is found in the atmosphere, the hydrosphere, the crust and living organisms.About 20% of the atmosphere formed diatomic molecules of oxygen.In the stratosphere at an altitude of about 12-50 km from the Earth's surface is a layer called "ozone shield".Its composition reflects the formula O3.Ozone protects our planet intensely absorbing harmful rays of 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 modification of oxygen, with significant differences in the spread in nature.
How to get oxygen and ozone?
molecular oxygen - the most important simple substance on Earth.Formed in the green parts of plants to light in the process of photosynthesis.When electrical discharges of natural or artificial origin diatomic molecule of oxygen breaks.The temperature at which the process is started, is about 2000 ° C.Part radicals arising connected again to form oxygen.Some active species react with diatomic molecules of oxygen.In this reaction, ozone is obtained, which also reacts with oxygen free radicals.Herewith the diatomic molecule.Reversible reaction results in the fact that the concentration of atmospheric ozone constantly changing.The formation of stratospheric layer consisting of O3 molecules, related to solar UV radiation.Without this shield the dangerous rays could reach the surface of the Earth and destroy all life forms.
allotropic modification of oxygen and sulfur
Chemical elements O (Oxygenium) and S (Sulfur) located in the same group in the periodic table, they are characterized by the formation of allotropes.From molecules with different numbers of atoms of sulfur (2, 4, 6, 8) under normal conditions, the most stable - S8, to the form of the crown.Rhombic and monoclinic sulfur are constructed of such 8-atom molecule.
At a temperature of 119 ° C the monoclinic form of yellow brown viscous mass forms - plastic modification.The study of allotropic modifications of sulfur and oxygen is important in theoretical chemistry and practical activities.
in industrial scale used oxidizing properties of different forms.Ozone is used for disinfection of air and water.However, at concentrations above 0.16 mg / m3 of this gas is harmful to humans and animals.Molecular oxygen is required for respiration, it is used in industry and medicine.An important role in economic activity played allotropes of carbon (diamond, graphite), phosphorus (white, red) and other chemical elements.
