CONTENTS

INTRODUCTION

Chemistry is a science about elements and the changes they undergo. It belongs to the list of fundamental natural sciences. Chemical knowledge and chemical practice (as an occupation) go back centuries. This way, occupations based on using the processes of animal skin treatment and producing leather using tanning materials, fabric dyeing with natural dyes, smelting metals (iron, copper) from metallic ore, making alloys (bronze), glass smelting, and potting appeared in various regions of the ancient world (Egypt, China, India) long before our era. It is not known where and when the first trades originated, but the results of archeological excavations and research provide us with insight into their spread in the ancient world. Primitive chemical knowledge definitely stems from the ancient times.

The trades and culture developed, the life conditions improved, the number of new applied trades and even industries continuously grew according to human needs becoming more diverse, even though there was no scientific notation of elements and their changes at that time.

The origin of the word "chemistry" is often connected to the name of the Ancient Egypt — "Chem", which means "dark", "black" (it must be related to the color of earth in the valley of the Nile River); the meaning of this name is "Egyptian science". Some historians think that this word came from the ancient Greek word "chymeia" — the art of metal smelting (from "chymos" — liquid, juice). The modern name of the science comes from Late Latin word "chimia" and is international, for instance, Chemie in German, chimie in French, and chemistry in English.

The ancients thought that there were four basic elements: fire, water, air, and earth (Aristotle). During the first centuries A.D. a specific phenomenon which was called alchemy formed in human culture and started developing. It combined the elements of theoretic philosophical schemes and practical knowledge used by chemical trades. Fruitless search of a so-called philosophers stone, which would allow turning any metal into gold, laid in the basis of alchemists' work.

Starting from the Renaissance era chemical research was to a greater extent dedicated to practical needs: metallurgy and glasswork, pottery and ink making were developing at an accelerating pace. The best known works were created by an Italian alchemist, metallurgist and architect V. Biringuccio (1481-1539), a German scientist G. Agricola (1494-1555), and a French natural scientist В. Palissy (1510-1589). A special branch of alchemy — iatrochemistry (comes from the ancient Greek word "iatros" — doctor) appeared in 16-17^th centuries due to the growth of cities and development of epidemics. It was trying to use chemistry for medical purposes with the main goal of creating medicines. This branch of science was practiced by such scholars as a Swiss alchemist and natural scientist Paracelsus (1493-1541), a Dutch chemist, physiologist and doctor J. van Helmont (1580-1644), etc.

The new approach to chemistry is connected to English and Irish physicist, chemist, natural philosopher and theologian R. Boyle (1627-1691), who proved inconsistency of the idea of so-called basic elements and for the first time created a scientific definition of a chemical element as the limit of decomposing substances into integral parts in 1661. The first theory used in the process of chemistry development up to the middle of the 18^th century was the phlogiston theory — the incorrect postulate that all bodies contained a special fire-like element. Despite being incorrect, this theory gave the first general explanation of the wide range of chemical changes connected to the processes of metal roasting and burning.

Russian natural scientist M.V. Lomonosov (1711-1765) was the first one to formulate the conservation of mass in chemical reactions in 1748. In 1756 he confirmed it experimentally using the example of metals being roasted in sealed vessels and discovered that burning and oxidation occur due to the interaction of the oxidized substance with air particles. In 1774-1777 a French chemist A. Lavoisier (1743-1794) proved that a certain integral part of air — oxygen — participated in this interaction. Chemistry became an exact and quantitative science right after this law was discovered.

A branch of chemistry related to extraction and use of natural ores and minerals became widespread by the end of the 18^th century and the beginning of the 19^th century.

This, in turn, particularly led to the discovery of new chemical elements like nickel (Ni), manganese (Mn), fluorine (F), chlorine (Cl), molybdenum (Mo), tungsten (W), tellurium (Те), chromium (Cr), uranium (U), beryllium (Be), yttrium (Y), and zirconium (Zr). About 20 chemical elements were discovered later using chemico-analytical methods. The research of gases gained widespread use and led to determination of the basic composition of Earth atmosphere and discovery of such elements as hydrogen (H), nitrogen (N), and oxygen (O). Carbon dioxide (CO₂), carbon monoxide (CO), nitrogen oxides (like NO), ammonia (NH₃), sulfur oxides (like sulfur dioxide SO₂), etc. were also discovered and characterized.

The next stage of the history of chemistry, which took almost the whole 19th century, is characterized by the development of theoretical basics of the science grouped around atomic theory. A revolution in chemistry happened thanks to a English chemist J. Dalton (1766-1844) who brought back to life the notions of intermittent (discrete) structure of matter and put forth the atomic theory in experimentally justified form in 1803. Dalton gave chemical elements a quantitative characteristic — the atomic mass. He also formulated the law of multiple proportions — if two elements form more than one compound between them, then the ratios of the masses of the first element which combine with a fixed mass of the second element will be ratios of whole numbers. In 1808 a French chemist J. Proust (1754-1826) proved a very important law of definite proportions — despite the type of its formation each certain chemical compound consists of the same elements with the constant ratio of their masses, and the relative number of atoms are expressed in whole numbers.

An Italian scientist A. Avogadro (1776-1856) gave a clear separation of the concepts of atom and molecule. In 1811 he discovered a law which formed the basis of determination of molecular masses of substances — equal volumes of gases (V) under the same conditions (temperature Г and pressure P), have the same number of molecules, meaning that one mole of any gas takes up the same volume under the same conditions. In particular, under normal conditions, meaning 0 °C (273 K) and 101.3 kPa, the volume of 1 mole of gas equals 22.413 (962) L (L/mol). This law made it possible to determine the molecular mass of a certain gas.

A so-called unitary system of Avogadro, based on the concept of a molecule as a single whole formed by the atoms of chemical elements, was created in 1840-s. This concept was proposed by French chemists A. Laurent (1807-1853), С Gerhardt (1816-1856), and J.B. Dumas (1800-1884). Together with the Avogadro's law this system allowed to separate the concepts of atom, molecule, and equivalent from each other. Approval and spread of the atomic theory is greatly attributable to a Swedish chemist J. Berzelius (1779-1848), whose work dated 1814 included the information about atomic weights of 46 elements as parts of about 2000 compounds. In 1853 Gerhardt presented a complete theory of types. According to this theory all substances are built like few inorganic compounds, or types, and can be derived from the latter by substitution of hydrogen atoms by atoms of other elements or radicals. The atomic theory was definitively approved after the first international chemical conference in Karlsruhe (1860) and formed the basis of the atomic and molecular theory, as for the atomic masses determined using the Avogadros law — they became commonly accepted.

The use of electric current for dissociation of complex chemical compounds can be considered the greatest achievement in chemistry of the early 19th century. This method allowed a British physician, chemist and inventor H. Davy (1778-1829) to discover new elements: potassium (K), sodium (Na), calcium (Ca), strontium (Sr), barium (Ba), and magnesium (Mg). Berzelius also used electric current for dissociation of substances and arrived at the conclusion that all of them contain two types of electricity — positive and negative. Using the dualistic system described by him (1812-1819), which explained the chemical affinity by electrostatic attraction of particles, he created the first classification of elements and their compounds. Discovery of the connection between electric and chemical phenomena played a great role in the subsequent development of a theory about the nature of chemical forces.

After the notion of "chemical element" was established and the basics of chemical atomism were laid, research of the dependence of chemical compounds' characteristics on their composition became the main goal of chemistry. In 1852 a British chemist E.E. Frankland (1825-1899) introduced the idea of valence of chemical elements.

Theory of chemical composition discovered a new principle in chemistry giving the opportunity to not only explain, but also to predict possible directions of reaction, to make conclusions about its mechanisms, as well as to pre-estimate the existence of new compounds and to carry out their systematic synthesis.

The beginning of use of spectral analysis in chemistry occurred in early 1860-s. Its first result was the discovery of new elements — rubidium (Rb), caesium (Cs), indium (In), and tantalum (Та). The number of known chemical elements at that time exceeded 60, the properties of many of them were fairly well studied, and their atomic masses were determined with a greater or lesser extent of correctness.

All this created the background for D.I. Mendeleyev's discovery of a fundamental law of nature— the periodic law of chemical elements — in 1869 and the development of their natural classification — the periodic system of elements, which revealed the interconnection of the elements and allowed to predict the existence and properties of those elements that have not been discovered yet.

The second half of the 19th century is also significant for the history of chemistry because during that period, especially starting from late 1870-s, physical chemistry formed a separate field. The end of the 19th century was marked by the outstanding discoveries in physics. In 1895 a German physicist W. Roentgen (1845-1923) discovered X-rays; a French physicist A. Becquerel (1852-1908) discovered the radioactivity phenomenon in 1896; a British physicist J. Thomson (1856-1940) and a German physicist E. Wiechert (1861-1928) discovered the electron in 1897 independently from each other; a British physicist W. Ramsay (1852-1926) discovered noble gases (neon (Ne), krypton (Kr), xenon (Xe), helium (He) in 1894-1898. These discoveries eventually led to essentially new notions of matter structure and characteristics. In 1911 a British physicist E. Rutherford (1871-1937) developed a nuclear (planetary) model of atom's structure. The quantum theory of a German theoretical physicist M. Planck (1858-1947), the pioneer of quantum physics, was used by a British physicist N. Bohr (1885-1962), who applied it to Rutherford's model, presented a structure model of atoms' electronic shells in 1913-1921, and in doing so lay the foundation of the periodic system theory. The atomic model not only became the central concept of atomism in the 20th century, but also became the basis of many chemical theories, including electronic concepts of chemical bonding, which were proposed by a German chemist W. Kossel (1888-1934) and the American physicist and chemist G. Lewis (1875-1946) in 1916.

The research of radioactivity helped to discover new radioactive elements: polonium (Po), radium (Ra), astatine (At), radon (Rn) (a French chemist Marie Curie, 1867-1934), as well as their isotopism; this course led to the formation of a new discipline — radiation chemistry. The advances in chemistry in the end of the 19^th century lay the foundation for a modern stage of this sciences development.

By the 20^th century chemistry formed as an indispensible and fundamental field of natural science. Currently it forms a very extensive area of human knowledge and plays a key role in economy.

By the 20^th century the needs of society led to the formation of a chemical technology which transfers from the use of natural substances and materials existing in nature through their more and more complex modification to the manufacturing of new chemical products not found in nature. More and more chemical elements (up to and including transuranic elements) are being involved in the production sphere, a more complete complex processing of natural substances is being achieved, the plans are developed for the use of such sources of raw materials as the World ocean. Intense chemical influence on the natural processes often leads to the disruption of existing ecological cycles, which adds additional challenge to the problem of preservation and scientific regulation of life environment of humans and society.

Due to the fact that all practical activity of mankind is connected to the use of matter as a material, chemical knowledge is crucial for all fields of science and technology utilizing with the material world. It is just like M.V. Lomonosov said in the past: "Chemistry spreads its arms wide and into human deeds..."