From our article you will learn what allotropy is. This concept is widespread in nature. For example, oxygen and ozone are substances consisting only of a chemical element of oxygen. How is this possible? Let's get it together.
Definition of a concept
Allotropy is the phenomenon of the existence of one chemical element in the form of two or more simple substances. Jens Berzelius, a chemist and minerologist from Sweden, is considered to be its discoverer. Allotropy is a phenomenon that has much in common with crystal polymorphism. 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 Allotropy
Not all chemical elements can form several simple substances. The ability to allotropy is due to the structure of the atom. Most often, it occurs in elements with a variable oxidation state. These include semi- and non-metals, inert gases and halogens.
Allotropy can be due to several reasons. These include a different number of atoms, the order of their combination into a molecule, the parallel spins of electrons, the type of crystal lattice. Consider these types of allotropy on specific examples.
Oxygen and ozone
This type of allotropy is an example of how a different number of atoms of one chemical element determines the physical and chemical properties of a substance. This also applies to the physiological effect on living organisms. So, oxygen consists of two oxygen atoms, ozone - of three.
What are the differences between these substances? Both are gaseous. Oxygen has no color, taste or smell; it is one and a half times lighter than ozone. This substance is well soluble in water, and with decreasing temperature the speed of this process only increases. Oxygen is essential for all organisms to breathe. Therefore, this substance is vital.
Ozone has a blue color. Each of us felt its characteristic smell after rain. It is sharp, but rather pleasant. Compared to oxygen, ozone is more chemically active. What is the reason? Upon decomposition of ozone, an oxygen molecule and a free oxygen atom are formed. He immediately enters into the reaction of the compound, forming new substances.
The amazing properties of carbon
But the number of atoms in a carbon molecule always remains unchanged. Moreover, 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 the atoms in the diamond are bonded by strong covalent bonds in all directions. Together, they form a three-dimensional network of tetrahedrons.
In graphite, strong bonds are formed only between atoms 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, every time we draw with a simple pencil on paper, a gray mark remains on it. This is the carbon layer.
Allotropy of sulfur
The reason for the sulfur modifications also lies in the peculiarities of the internal structure of the 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 includes 8 atoms. According to its physical properties, rhombic sulfur is a yellow solid. It is not only insoluble in water, but not even wetted by it. Indices of thermal and electrical conductivity are very low.
The structure of monoclinic sulfur is represented by a parallelepiped with beveled corners. Visually, this substance resembles dark yellow needles. If sulfur is melted and then placed in cold water, a new modification is formed. Its original structure will collapse to polymer chains of different lengths. So get plastic sulfur - a rubbery mass of brown.
Phosphorus modifications
Scientists have 11 types of phosphorus. His allotropy was discovered almost by accident, like this substance itself. In search of a 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. Enough to raise the temperature to 40 degrees, so that white phosphorus reacts with oxygen and ignites.
For phosphorus, the cause of allotropy is a change in the structure of the crystal lattice. 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 typical for it to glow. When heated, it turns into steam. We observe this every time, lighting ordinary matches. The grinding surface just contains red phosphorus.
So, allotropy is the existence of one chemical element in the form of several simple substances. Most often found among non-metals. The main reasons for this phenomenon are considered to be a different number of atoms forming a molecule of a substance, as well as a change in the configuration of the crystal lattice.