allotrope is the ability of atoms of one element to form different types of simple substances.Thus the formation of compounds that differ from each other.
allotropic modifications are stable.Under constant pressure at a certain temperature, these substances can pass one into another.
allotropic modifications may be formed from molecules having a different number of atoms.For instance, an oxygen forms ozone (O3) and the actual substance oxygen (O2).
allotropic modifications may be solids having a different crystal structure.Such compounds include, for example, diamond and graphite.These substances - allotropic modification of carbon.This chemical element can form five simple substances: hexagonal and cubic diamond, graphite, carbyne (two forms).
hexagonal diamond discovered in meteorites and obtained in the laboratory by prolonged heating under the influence of very high pressure.
diamond, as is known, is the hardest of all substances that exist in nature.It is used in the drilling of rocks and glass cutting.Diamond is transparent colorless crystalline substance which has a high svetoprelomlyaemostyu.Diamond crystals have a face-centered cubic lattice.Half of the atoms in the crystal is located at the centers of the faces and vertices of the cube, and the other half of the atoms - in the centers of the faces and the top of each cube, which is offset relative to the first in the direction of the space diagonal.Tetrahedral atoms form a three-dimensional grid in which they have a covalent bond.
Of all the simple substances is present only in the diamond maximum number of atoms, which are located very close.Therefore, the compound is very strong and solid.Strong communication carbon tetrahedra provide a high chemical resistance.At diamond can affect only fluorine or oxygen at a temperature of eight degrees.
without air heating with a strong diamond is transformed into graphite.This material is presented crystals dark gray.Graphite has a weak metallic luster.At the touch of an oily substance.Graphite is stable to heat, has a relatively high thermal and electrical conductivity.The substance used in the manufacture of pencils.
Carbine prepared synthetically.This solid black glass gloss.Without access to air under heating carbyne converted into graphite.
There is another form of carbon - amorphous carbon.This disordered structure obtained by heating carbon-containing compounds.Large deposits of coal are found in nature.When this material has several varieties.Coal can be represented in the form of soot, bone char, or coke.
As already mentioned, allotropic modification of one element are characterized by different interatomic structure.Furthermore, they are endowed with different chemical and physical properties.
Sulfur is another element capable of allotropy.This substance is used by man since ancient times.There are different allotropic modifications of sulfur.The most popular is rhombic.It is represented by a yellow solid.Rhombic sulfur is not wetted by water (swimming at the surface).This property is used in the extraction of the substance.Rhombic sulfur is soluble in organic solvents.The substance has a low electrical and thermal conductivity.
In addition, there is a plastic and monoclinic sulfur.The first is a brown amorphous (like rubber) weight.It is formed, if cold water pour molten sulfur.Monoclinic represented as dark yellow needles.Under the influence of the room (or approximated) either temperature pass these modifications into the rhombic sulfur.
