From our article you will learn what allotropy.This concept is widespread in nature. For example, oxygen and ozone are substances that consist only of the chemical element oxygen. How is this possible? Let's figure it out together.
Definition of concept
Аллотропией называют явление существования одного chemical element in the form of two or more simple substances. His discoverer is rightly considered a chemist and a minerologist from Sweden, Jens Berzelius. Allotropy is a phenomenon that has much in common with a polymorphism of crystals. This caused a lot of controversy among scientists. Currently, they have come to the conclusion that polymorphism is characteristic only of solid simple substances.
Causes of Allotropia
Forming a few simple substances may notall chemical elements. The ability to allotropy due to the structure of the atom. Most often it is found in elements that have a variable degree of oxidation. These include semi- and non-metals, inert gases and halogens.
Allotropy may be due to severalreasons. These include a different number of atoms, the order of their connection into a molecule, the parallelism of the electron spins, the type of crystal lattice. Consider these types of allotropy with specific examples.
Oxygen and Ozone
This type of allotropy is an example of how differentthe number of atoms of a single chemical element determines the physical and chemical properties of a substance. This also applies to the physiological effects on living organisms. So, oxygen consists of two atoms of oxygen, ozone - of three.
What is the difference between these substances?Both are gaseous. Oxygen has no color, taste and smell, it is one and a half times lighter than ozone. This substance is highly soluble in water, and with a decrease in temperature, the rate of this process only increases. Oxygen is necessary for all organisms to breathe. Therefore, this substance is vital.
Ozone is blue.Its characteristic smell was felt by each of us after the rain. It is sharp, but quite pleasant. Compared to oxygen, ozone is more chemically active. What is the reason? The decomposition of ozone produces an oxygen molecule and a free oxygen atom. He immediately enters into the reaction of the compound, forming a new substance.
The amazing properties of carbon
But the number of atoms in the carbon moleculealways stays the same. At the same time, it forms completely different substances. The most common carbon modifications are diamond and graphite. The first substance is considered the hardest on the planet. This property is due to the fact that atoms in diamond are bound by strong covalent bonds in all directions. Together, they form a three-dimensional network of tetrahedra.
In graphite, strong bonds are formed only betweenatoms located in the horizontal plane. For this reason, breaking a graphite rod along is almost impossible. But the bonds that connect the horizontal layers of carbon to each other are very weak. Therefore, each time we draw a simple pencil over the paper, a gray trace remains on it. This is the carbon layer.
Sulfur Allotropy
The reason for the modifications of sulfur is alsofeatures of the internal structure of molecules. The most stable form is rhombic. The crystals of this type of sulfur allotropy are called rhomboidal. Each of them is formed by corona-shaped molecules, each of which consists of 8 atoms. Physically, rhombic sulfur is a yellow solid. Not only does it not dissolve in water, but it is not even wetted by it. Thermal and electrical conductivity rates are very low.
The structure of monoclinic sulfur is represented byparallelepiped with beveled corners. Visually, this substance resembles dark-yellow needles. If sulfur is melted and then placed in cold water, a new modification of it is formed. Its original structure will collapse to polymer chains of different lengths. So get plastic sulfur - rubbery mass of brown.
Phosphorus modifications
Scientists have 11 types of phosphorus.His allotropy was discovered almost by accident, like the substance itself. In search of the philosopher's stone, the alchemist Brand received a luminous dry substance as a result of evaporation of urine. It was white phosphorus. This substance is characterized by high chemical activity. It is enough to raise the temperature to 40 degrees so that the white phosphorus reacts with oxygen and ignites.
For phosphorus, the cause of allotropy is a change inlattice structure. You can change it only under certain conditions. So, increasing the pressure and temperature in the atmosphere of carbon dioxide, get red phosphorus. Chemically, it is less active, so it is not characteristic glow. When heated, it turns into steam. We see it every time, lighting ordinary matches. The grated surface just contains red phosphorus.
So allotropy is the existence of onechemical element in the form of several simple substances. Most common among non-metals. The main causes of this phenomenon are considered to be a different number of atoms forming a substance molecule, as well as a change in the configuration of the crystal lattice.
