lot of different things and objects, animate and inanimate bodies of nature around us.And they all have their composition, structure, properties.In living beings proceed complicated biochemical reactions that accompany the processes of life.Lifeless body perform different functions in nature and living biomass are complex molecular and atomic structure.
But with the objects of the planet have a common feature: they are composed of many tiny structural particles called atoms of chemical elements.So small that the naked eye does not see them.What is the chemical elements?What are the characteristics they have and how it became aware of their existence?Try to understand.
concept of chemical elements
in the conventional sense chemical elements - this is just a graphical display of the atoms.The particles that make up everything that exists in the universe.That is the question "what is the chemical elements" can give an answer.This small complex structures, all isotopes of atoms together, united by a common name, with its graphic symbol (symbol).
Today we know of 118 elements, which are open both in the wild and synthetically, through the implementation of nuclear reactions and radioactive decays of nuclei of other atoms.Each has a set of characteristics, its position in the overall system, and the name of the history of the discovery, and also performs a role in the nature and living beings.Study of these features is engaged in the science of chemistry.Chemical elements - is the basis for the construction of molecules both simple and complex compounds, and thus chemical interactions.
History of discovery
very understanding of what chemical elements come only in the XVII century through the work of Boyle.It was he who first spoke about this concept and gave him the following definition.This small indivisible simple substance, of which there is everything, including all the complex.
Before this work was dominated by the views of the alchemists, accept the theory of the four elements - Empidokla and Aristotle, and open "start combustible" (sulfur) and "metal beginning" (mercury).
Almost all the XVIII century has been extended completely erroneous theory of phlogiston.However, at the end of this period, Antoine Lavoisier proved that it is untenable.He repeats the wording of Boyle, but complements it with the first attempt to systematize all known at that time elements, having distributed them into four groups: metals, radical land, non-metals.
next big step in understanding what chemical elements, making Dalton.He is credited with the discovery of atomic mass.On this basis, it distributes part of the known chemical elements in order of increasing atomic mass.
steadily rapid development of science and technology allows you to make a number of discoveries of new elements in the composition of natural bodies.Therefore, to 1869 - the time of the great creations of Mendeleev - science has learned about the existence of 63 elements.The work of the Russian scientist was the first complete and all-established classification of these particles.
structure of the chemical elements at the time has been set.It was believed that the atom is indivisible, it is the smallest unit.With the discovery of radioactivity it was proved that it is divided into the structural parts.Almost everyone at the same time is in the form of several natural isotopes (similar particles, but with a different number of neutrons structures, which varies from the atomic mass).Thus, by the middle of the last century, succeeded in determining the order of the concept of a chemical element.
System of chemical elements
based scientist put the difference in the atomic weight and has managed a brilliant way to arrange all the known chemical elements in order of increasing it.However, the depth and brilliance of his scientific thinking and foresight was that Mendeleyev left blank spaces on your system, open cells for yet unknown elements, which, according to the scientist, the future will be opened.
And everything turned out exactly as he said.Chemical elements over time filled all the empty cells.It was open every scientist predicted structure.And now we can safely say that the system of chemical elements is represented by 118 units.However, three recent discoveries not yet been officially confirmed.
itself of chemical elements displayed graphically table, in which the elements are arranged according to the hierarchy of their properties, the charges of the nuclei and characteristics of the structure of the electron shells of their atoms.So, there are periods (7 pieces) - horizontal rows, groups (8 pieces) - vertical subgroup (main and sideline within each group).In most cases, a separate table in the lower layers of the two rows are carried families - the lanthanides and actinides.
Mendeleev's periodic system contains all the necessary information about the chemical elements (sequence number, the mass number, the name, sometimes the last layers of the electronic structure).
Names
right to give the name given to the person who made the discovery of the chemical element.Many are named after planets (uranium, plutonium, neptunium).Another was given the name in honor of the great scientists (mendelevium Rutherford, Copernicium and others).
Most items are named after cities and countries (ruthenium, germanium, Dubna, France, Europe and others).Sending even serve as mythical heroes (promethium).It is also common phenomenon when a particular name is given on the properties exhibited by both simple and complex substances of this element (hydrogen, oxygen, carbon).
names are written in Latin, but in our country there is a Russian translation with entrenched pronunciation.The symbol of each element is considered to be the first letter of the Latin word, or the first and any subsequent.Example: calcium (Ca) - Calcium, boron (B) - Boron.
characteristics of atoms of chemical elements
A representative of the periodic system has the features of both the structure and in showing the properties.Characteristic chemical analysis element composed of the composition of the nucleus and its electronic layers as well as the definition of a simple substance, they are formed, and complex compounds.
composition of the nuclei of atoms of chemical elements includes several particle - nucleon:
- protons, which determine its positive charge (p + 1), and part of the atomic mass;
- neutrons affecting the mass number of the element and without charge (n0).
Another type of particles - electrons.They move around the nucleus and have a negative charge (e-1).Targeting them is not chaotic, but strictly ordered.They are located on the orbitals (s, p, d and f), which form the sublevels and levels (electronic layers).
atomic mass of the element made up of protons and neutrons, the totality of which is called "mass number".The number of protons is defined very simply - it is equal to the ordinal number of the element in the system.And as the atom as a whole - the system electrically neutral, that is, not having no charge at all, the number of negative electrons is always equal to the number of positive particles of protons.
Thus, characterization of the chemical element can be given by its position in the periodic system.Indeed, in almost all cell described: a sequence number, which means that electrons and protons, the atomic weight (the average value of all existing isotopes of the element).It can be seen, in which the structure is shown (which means that on so many layers, the electrons will be located).It is also possible to predict the number of negative particles in the last energy level for the main group elements - it is equal to the group number, in which the element is located.
number of neutrons can be calculated by subtracting from the mass of protons, ie serial number.Thus, we can get and make the whole electron-graphic formula for each chemical element to be exactly reflect its structure and to show the possible extent of oxidation and exhibit properties.
abundant element in nature
explore this issue deals with a science - cosmochemistry.The data show that the distribution of elements on the planet follows the same pattern in the universe.The main source of the nuclei of light, medium and heavy atoms are nuclear reactions occurring in stars - nucleosynthesis.Through these processes, the universe and outer space have provided our planet by all means chemical elements.
A total of 118 representatives in the known natural sources of natural persons were found 89. It is fundamental, the most common atoms.The chemical elements were synthesized artificially by bombarding nuclei with neutrons (nucleosynthesis in the laboratory).
considered most numerous simple substances of elements such as nitrogen, oxygen, hydrogen.Carbon is a part of all organic matter, and thus also holds a leading position.
Classification of the electronic structure of atoms
One of the most common classifications of all the chemical elements of the system - the distribution of them on the basis of the electronic structure.As to how much of the energy levels is part of the shell of the atom, and which of them contains the latest valence electrons, it is possible to distinguish four groups of elements.
S-elements
It is those in which the latter is filled s-orbital.This family includes the elements of the first group of the main group (or alkali metal).A single electron in the outer level defines the similar properties of the representatives of both strong reducing agents.
P elements
total of 30 pieces.The valence electrons are arranged on the p-sublevel.These are the elements that form the main subgroups of the third to eighth group related to 3,4,5,6 periods.Among these properties are found both metals and typical metallic elements.
d-and f-elements elements
This transition metals from 4 to 7 a long period.A total of 32 elements.Simple substances can exhibit both acidic and basic properties (oxidation and reduction).Also, amphoteric, that is ambivalent.
to the f-family includes the lanthanides and actinides, in which the electrons are placed last on the f-orbitals.
substances formed elements: simple
Also, all classes of chemical elements can exist in the form of simple or complex compounds.Thus, simple considered to be those which are formed from the same structure in different amounts.For example, O2 - Oxygen or dioxygen and O3 - ozone.This phenomenon is called allotropy.
Simple chemical elements that form connections of the same name, characteristic of every member of the periodic system.But not all of them are equal in showing the properties.Thus, there are simple substance metals and nonmetals.The first images of the main sub-groups with 1-3 group and all subgroups of the side table.Non-metals also form a major subgroup of 4-7 teams.The eight core includes special elements - the noble or inert gases.
Among all open today simple elements known under normal conditions of 11 gas 2 liquid substances (bromine and mercury), all others - solid.
complex compounds
To those accepted to all, which consist of two or more chemical elements.Examples of mass, because of chemical compounds known to more than 2 million!It salts, acids, bases and acids, complex complexes, all organic matter.
