definition
If the word "chemistry" is interpreted literally, it is "the science of change". Chemistry, like physics, is the basic science of natural science. Chemistry is a natural science based on experiments. Many people call chemistry "central science" because chemistry is the core of some scientific disciplines, such as materials science, nanotechnology, biochemistry and so on. Chemistry is a science that studies the composition, structure, properties and changing laws of substances at the atomic level, which is also the core basis of chemical changes. There are five and two disciplines in modern chemistry: inorganic chemistry, organic chemistry, physical chemistry, analytical chemistry and polymer chemistry. [ 1]
trait
Chemistry is one of the important basic sciences and a subject based on experiments. It develops rapidly with the mutual penetration of physics, biology, geography, astronomy and other disciplines, and also promotes the development of other disciplines and technologies. For example, the research results of nucleic acid chemistry have raised today's biology from the cellular level to the molecular level and established molecular biology.
research objects
Chemistry plays an important role in our understanding and utilization of matter. The universe is made of matter, and chemistry is one of the main ways and means for human beings to understand and transform the material world. It is a discipline with a long history and full of vitality, which is closely related to human progress and social development, and its achievement is an important symbol of social civilization.
From the primitive society in which fire was used to the modern society in which various artificial substances were used, human beings are enjoying the fruits of chemistry. Human life can be continuously improved and improved, and the contribution of chemistry plays an important role in it.
research method
By analyzing the chemical composition of various stars, the distribution law of elements is obtained, and it is found that there are simple compounds in interstellar space, which provides experimental data for celestial evolution and modern cosmology and enriches the content of dialectics of nature.
2 Editing of Periodic Table of Elements
periodic table of elements
The periodic table of elements is the core of chemistry. The periodic table of elements is a concrete form of the periodic law of elements expressed in tables, which reflects the internal structure of elements and the law of their relationship. The periodic table of elements is called periodic table for short. The periodic table of elements has 7 periods, 16 families and 4 regions. The position of elements in the periodic table can reflect the atomic structure of elements. The same row of elements in the periodic table constitutes a period. The number of electron layers of atoms in the same period is equal to the ordinal number of the period. Elements in the same column (the eighth group includes three columns) are called "families". Groups are the reflection of electron shell configuration inside and outside atoms. For example, for external electronic configuration, family IA is ns 1, family IIIA is ns2np 1, family O is ns2np4, and family IIIB is (n- 1) D 1 NS2, etc. The periodic table of elements can vividly reflect the periodic law of elements. According to the periodic table of elements, we can infer the atomic structure of various elements and the gradual change law of the properties of elements and their compounds. At that time, Mendeleev successfully predicted the properties of unknown elements and their compounds according to the properties of surrounding elements and compounds of unknown elements in the periodic table. Now, scientists use the periodic table to guide the search for elements and compounds used to make semiconductors, catalysts, chemical pesticides and new materials.
The periodic law of elements in modern chemistry is 1869 by Russian scientist Dmitri Ivanovich Mendeleev.
First of all, he arranged the 63 elements known at that time in the form of table according to atomic weight, and put the elements with similar chemical properties in the same row, which is the prototype of the periodic table of elements. Using the periodic table of elements, Mendeleev successfully predicted the characteristics of elements (gallium, scandium and germanium) that had not been discovered at that time. 19 13 British scientist Moseler used cathode rays to hit metals to generate X-rays, and found that the greater the order of atoms, the higher the frequency of X-rays. Therefore, he believes that the positive charge of the nucleus determines the chemical properties of the elements, and arranges the elements according to the positive charge in the nucleus (that is, the number of protons or the atomic order), which has become the contemporary periodic table after years of revision.
3 history editor
abstract
The historical origin of chemistry is very old. It can be said that the earliest chemical practice began when humans learned to use fire. Our ancestors drilled wood for fire, roasted food with fire, kept warm in cold nights and drove away wild animals, making full use of the phenomena of light and heat during burning. At that time, it was just the accumulation of experience. The formation of chemical knowledge and the development of chemistry have gone through a long and tortuous road. It develops with the progress of human society and is the inevitable result of social development. Its development has promoted the development of productive forces and historical progress. The development of chemistry has mainly experienced the following periods:
germination period
From ancient times to BC 1500, humans learned to make pottery with clay, burn metal with ore, make wine with grain, and dye fabrics such as silk and flax with fire. These are the earliest chemical processes that have not formed chemical knowledge after a long period of exploration under the direct inspiration of practical experience, but they are just the embryonic stage of chemistry. In ancient times, in order to survive, primitive humans discovered and used fire in the struggle against various disasters in nature. Primitive humans began to use fire, from barbarism to civilization, and at the same time began to understand and transform natural substances by chemical methods. Combustion is a chemical phenomenon. The discovery and utilization of fire has improved the living conditions of human beings and made them smart and powerful. After mastering fire, humans began to eat cooked food; Then humans discovered some material changes one after another. For example, burning charcoal fire on emerald malachite and other copper ores will produce red copper. In China, the bronze society began to transform during the Spring and Autumn Period and the Warring States Period, and the social changes triggered by the iron Niu Geng promoted the development of chemistry. [2]
In this way, in the process of gradually understanding and utilizing the changes of these substances, human beings have made products of use value to human beings. Humans gradually learned to make pottery and smelt; Later, I learned wine making, dyeing and so on. These products, which are processed and transformed from natural materials, have become symbols of ancient civilization. On the basis of these production practices, ancient chemical knowledge sprouted.
Dan medicine period
From about 1500 BC to 1650 AD, chemistry was controlled by alchemy and alchemy. In order to obtain immortal elixir or gold symbolizing wealth, alchemists and alchemists began the earliest chemical experiments, and then books recording and summarizing alchemy appeared one after another. Although both alchemists and alchemists ended in failure, in the process of refining elixir and exploring the method of "turning stone into gold", they realized the mutual transformation between substances by artificial methods, accumulated the conditions and phenomena of chemical changes of many substances, and accumulated rich practical experience for the development of chemistry. The word "chemistry" that appeared at that time meant "alchemy". But with the decline of alchemy and alchemy, people see its absurd side more and more. In fact, chemical methods have been properly played in medicine and metallurgy, and the development of pharmacology and metallurgy at home and abroad has prepared rich materials for chemistry to become a science. At the same time, the properties of various substances, especially the properties of mutual reaction, are further classified and studied. All these laid the foundation for the emergence of modern chemistry, and many instruments and methods are still used in today's chemical experiments after improvement. An alchemist invented gunpowder in his experiment, discovered some elements, made some alloys, and made and purified many compounds. These achievements are still in use today.
Phlogiston period
This period, from 1650 to 1775, is the gestation period of modern chemistry. With the accumulation of metallurgical industry and laboratory experience, people sum up perceptual knowledge and make theoretical research on chemical changes, making chemistry a branch of natural science. British chemist Boyle pointed out the scientific concept of chemical elements, which marked the beginning of this stage. Then chemistry was liberated from alchemy by phlogiston. According to phlogiston theory, combustible can burn because it contains phlogiston, and the combustion process is the process in which combustible releases phlogiston. Although this theory is wrong, it unifies a large number of chemical facts under one concept and explains many chemical phenomena. During the more than one hundred years when phlogiston theory prevailed, chemists did a lot of experiments to explain various phenomena, discovered the existence of various gases, and accumulated more new knowledge about substance transformation. In particular, phlogiston theory holds that chemical reaction is a process of transferring one substance to another, and substances are conserved in chemical reaction, which lays the foundation of modern chemical thought. This period not only prepared for the development of modern chemistry in scientific practice, but also in thought, and became the gestation period of modern chemistry. /kloc-Since the beginning of the 6th century, industrial production in Europe has flourished, which has promoted the establishment and development of pharmaceutical chemistry and metallurgical chemistry. Make alchemy turn to life and practical application, and then pay more attention to the study of substance and chemical change itself. After the scientific concept of elements was established, the scientific oxidation theory and the law of mass conservation were established through the accurate experimental study of combustion phenomenon, and then the law of constant ratio, law of multiple proportions and the law of combined quantity were established, which laid the foundation for the further scientific development of chemistry.
period of expansion
This period, from 1775 to 1900, is a period of modern chemistry development. 1775 or so, lavoisier expounded the oxidation theory of combustion with quantitative chemical experiments, which initiated the period of quantitative chemistry and made chemistry develop along the right track. /kloc-At the beginning of the 9th century, British chemist Dalton put forward modern atomism, emphasizing that the atomic mass of various elements is its most basic feature, and the introduction of the concept of quantity is a big difference from ancient atomism. Modern atomism made the chemical knowledge and theory at that time reasonably explained and became a unified theory to explain chemical phenomena. Then, the Italian scientist Avo Gardero put forward the concept of molecule. Since atomic and molecular theories were used to study chemistry, chemistry has really been established as a science. During this period, many basic laws of chemistry were established. Russian chemist Mendeleev discovered the periodic law of elements, while German chemists Justus von Liebig and Willer developed the theory of organic structure, which made chemistry a systematic science and laid the foundation for the development of modern chemistry.
/kloc-In the second half of the 9th century, after introducing physical theories such as thermodynamics into chemistry, not only the concepts of chemical equilibrium and reaction rate were clearly defined, but also the direction and conditions of substance transformation in chemical reactions could be quantitatively judged. The theoretical foundations of solution theory, ionization theory, electrochemistry and chemical kinetics have been established one after another. The birth of physical chemistry raised chemistry to a new level in theory. Through the analysis of minerals, many new elements have been found, and with the experimental verification of atomic and molecular theory, the classical chemical analysis method has its own system. The synthesis of oxalic acid and urea, the emergence of the concept of valence, the establishment of the six-ring structure of benzene and the tetrahedron of carbon valence bond, the resolution of tartaric acid into optical isomers, and the discovery of molecular asymmetry have led to the establishment of the theory of organic chemical structure, deepened people's understanding of molecular essence and laid the foundation of organic chemistry.
Modern Times
Chemistry in the 20th century is a science based on experiments. Experiment and theory have always been interdependent and mutually promoting aspects in chemical research. After entering the 20th century, influenced by the development of other disciplines of natural science, the theories, techniques and methods of contemporary science have been widely used. Chemistry has made great progress in understanding the composition, structure, synthesis and testing of substances, and has made many important achievements in theory. On the basis of inorganic chemistry, analytical chemistry, organic chemistry and physical chemistry, a new branch of chemistry has emerged.
The application of modern physical theory and technology, mathematical methods and computer technology in chemistry has greatly promoted the development of modern chemistry. At the end of 0/9, the discovery of electrons, X-rays and radioactivity created conditions for the great progress of chemistry in the 20th century.
In structural chemistry, the modern nucleated atom model established by the discovery of electrons not only enriches and deepens the understanding of the periodic table of elements, but also develops the molecular theory. Applying quantum mechanics to study molecular structure.
From the study of the molecular structure of hydrogen, the nature of chemical bonds was gradually revealed, and valence bond theory, molecular orbital theory and coordination field theory were established successively. The theory of chemical reaction also goes deep into the microscopic field. Using X-ray as a new analytical method to study the structure of matter can provide insight into the crystal chemical structure of matter. There are three methods to determine the chemical three-dimensional structure: X-ray diffraction, electron diffraction and neutron diffraction. Among them, the application of X-ray diffraction method has accumulated the most accurate information of molecular three-dimensional structure.
Spectral methods for studying the structure of matter have also been extended from visible spectrum, ultraviolet spectrum and infrared spectrum to nuclear magnetic resonance spectrum, electron selective vibration spectrum, photoelectron spectrum, X-ray vibration spectrum, Mossbauer spectrum and so on. Combined with computer, a large number of materials related to material structure and performance have been accumulated, which are developing from experience to theory. With the increasing magnification of electron microscope, people can directly observe the structure of molecules.
Due to the discovery of radioactivity, the classical theory of elements has undergone profound changes. From the establishment of radioactive decay theory, the discovery of isotopes to the realization of artificial nuclear reaction and nuclear fission, the discovery of deuterium, neutrons, positrons and other basic particles, not only human understanding goes deep into the subatomic level, but also the corresponding experimental methods and theories are established; It not only realized the ancient alchemists' idea of changing elements, but also changed people's world outlook.
As a symbol of the 20th century, mankind began to master and use nuclear energy. Radiochemistry and nuclear chemistry appeared one after another and developed rapidly. Interdisciplinary disciplines such as isotope geology and isotope cosmochemistry have been born one after another. The periodic table of elements has been extended to 109, and overweight elements are being explored to verify the "stable island hypothesis" of elements. The theory of element origin, which depends on modern cosmology, and nuclide dating, which is closely related to evolution, are constantly supplementing and updating the concept of elements.
The synthesis of phenolic resin opens up the field of polymer science. With the synthesis of polyamide fiber in 1930s, the concept of polymer has been widely recognized. Later, the synthesis, structure and properties research and application of polymers constantly cooperated and promoted each other, which made polymer chemistry develop rapidly.
The synthesis and application of various polymer materials provide various important materials with excellent performance and low cost for modern industry and agriculture, transportation, medical and health care, military technology and people's daily necessities, and become an important symbol of modern material civilization. Polymer industry has developed into an important pillar of chemical industry. The 20th century is the golden age of organic synthesis. Great progress has been made in chemical separation methods and structural analysis methods. The structural problems of many natural organic compounds have been satisfactorily solved, and many new important organic reactions and specific organic reagents have been discovered. On this basis, fine organic synthesis, especially asymmetric synthesis, has made great progress.
On the one hand, various organic compounds with special structures and properties were synthesized. On the other hand, the basic substances of life, from unstable free radicals to bioactive protein and nucleic acids, were synthesized. Organic chemists have also synthesized natural organic compounds with complex structures and drugs with special effects. These achievements have greatly promoted the development of science; It provides favorable conditions for the synthesis of substances with high biological activity and the cooperation with other disciplines to solve the synthesis problems of biological substances and the chemical problems of prebiotics.
Since the 20th century, the development trend of chemistry can be summarized as: from macro to micro, from qualitative to quantitative, from stable to metastable, from experience to theory, and then used to guide design and pioneering research. On the one hand, provide as many new substances and materials as possible for the production and technical departments; On the other hand, in the process of mutual infiltration with other natural sciences, new disciplines are constantly emerging and developing in the direction of exploring life sciences and the origin of the universe.
4 subject classification editing
Overview of disciplines
Chemical changes: the production of other substances has changed (combustion, steel rust, food decay, grain brewing, animal and plant respiration, photosynthesis, etc.). ).
In the development of chemistry, according to the different types of molecules studied, the research methods, purposes and tasks are different, and many branches of different levels are derived. Before the 1920s, chemistry was traditionally divided into four branches: inorganic chemistry, organic chemistry, physical chemistry and analytical chemistry. Since the 1920s, due to the rapid development of the world economy, the birth of electronic theory and quantum mechanics of chemical bonds, and the rise of electronic technology and computer technology, chemical research has gained new means in theory and experimental technology, which has led to the rapid development and brand-new appearance of this discipline since the 1930s. The content of chemistry is generally divided into seven categories, including biochemistry, organic chemistry, polymer chemistry, applied chemistry and chemical engineering, physical chemistry and inorganic chemistry, with seven branches.
According to the development of chemistry today and its mutual penetration with astronomy, physics, mathematics, biology, medicine, earth science and other disciplines, chemistry can be classified as follows:
Specific branch
inorganic chemistry
Elemental chemistry, inorganic synthetic chemistry, inorganic polymer chemistry, inorganic solid chemistry, coordination chemistry (that is, complex chemistry), isotope chemistry, bioinorganic chemistry, organometallic chemistry, metalloenzyme chemistry, etc.
organic chemistry
General organic chemistry, organic synthetic chemistry, metal and nonmetal organic chemistry, physical organic chemistry, bioorganic chemistry, organic analytical chemistry.
physical chemistry
Structural chemistry, thermochemistry, chemical thermodynamics, chemical kinetics, electrochemistry, solution theory, interface chemistry, colloid chemistry, quantum chemistry, catalysis and its theory.
analytical chemistry
Chemical analysis, instrument and new technology analysis. Including performance measurement, monitoring, various spectral and photochemical analysis, various electrochemical analysis methods, mass spectrometry, various electron microscopes, imaging and morphology analysis methods, online analysis, activity analysis, real-time analysis and so on. Various detection methods of physical and chemical properties and physiological activities, separation methods such as extraction, ion exchange, chromatography and mass spectrometry, combined separation analysis, combined synthesis and separation analysis, etc. [3]
high polymer chemistry
Natural polymer chemistry, polymer synthetic chemistry, polymer physical chemistry, polymer application, polymer physics.
nuclear chemistry
Radioelement chemistry, radioactive analytical chemistry, radiochemistry, isotope chemistry, nuclear chemistry.
biochemistry
General biochemistry, enzyme, microbial chemistry, phytochemistry, immunochemistry, fermentation and bioengineering, food chemistry, coal chemistry, etc.
Other frontier disciplines related to chemistry include geochemistry, marine chemistry, atmospheric chemistry, environmental chemistry, cosmic chemistry, interstellar chemistry and so on.
5 green chemistry editor
foreword
Green chemistry, also known as "environment-friendly chemistry", "environment-friendly chemistry" and "clean chemistry", has been produced and developed in recent ten years.
New chemistry baby. It involves many subjects, such as organic synthesis, catalysis, biochemistry, analytical chemistry and so on. The biggest feature of green chemistry is that it uses scientific means to prevent pollution from the beginning, so the process and terminal are zero emissions or zero pollution. Many countries in the world regard "green chemistry" as one of the main directions of chemical progress in the new century.
definition
Chemical technology, principles and methods are used to eliminate toxic and harmful chemicals to human health, safety and ecological environment, so it is also called environment-friendly chemistry or clean chemistry. In fact, green chemistry is not a brand-new science.
Green chemistry not only has great social, environmental and economic benefits, but also shows that the negative effects of chemistry can be avoided, showing people's initiative. Green chemistry embodies the interrelation and interaction among chemical science, technology and society, is the product of the high development of chemical science and the role of society in the development of chemical science, and is the arrival of a new stage of chemistry itself. As a generation in the new century, we should not only have the ability to develop new and more environmentally friendly chemistry to prevent chemical pollution; It is also necessary for the younger generation to understand and accept and make due contributions to green chemistry.
Famous theory
1, "atomic economy", that is, make full use of every atom in the reactant, so as to make full use of resources and prevent pollution. The concept of atomic economy was put forward by Trost, a famous American organic chemist, in 1992 (for which he won the 1998 Presidential Green Chemistry Challenge Award).
The atomic economy of the reaction is measured by the atomic utilization rate. Efficient organic synthesis should make maximum use of every atom of the original molecule and combine it with the target molecule to achieve zero emission. Green organic synthesis should be atomic economy. The higher the utilization rate of atoms, the less waste generated by the reaction and the less pollution to the environment.
2. Its connotation is mainly embodied in five "R": the first is "reduction", that is, reducing the discharge of "three wastes"; Second, reuse-"reuse", such as catalysts and carriers in the chemical process, is the need to reduce costs and waste; Third, recovery-"recycling" can effectively achieve the requirements of "saving resources, reducing pollution and reducing costs"; Fourth, regeneration-"regeneration" is an effective way to turn waste into treasure, save resources and energy and reduce pollution; The fifth is to refuse.
-"Refusing to use" refers to refusing to use some irreplaceable raw materials with obvious toxic and side effects and pollution, which is the most fundamental method to eliminate pollution.
meaning
The traditional chemical industry has brought serious pollution to the environment, and the world produces 300 million to 400 million tons of harmful waste every year, which is harmful to the environment and threatens the survival of mankind. Whether the chemical industry can produce chemicals that are harmless to the environment, or even develop processes that do not produce waste, people of insight put forward the call for green chemistry, which immediately received positive responses from all countries in the world. The core of green chemistry is to eliminate pollution from the source by using chemical principles.
Green chemistry poses a new challenge to chemists and is highly valued internationally. From 65438 to 0996, the United States established the "Green Chemistry Challenge Award" to commend those enterprises and scientists who have made outstanding achievements in the field of green chemistry. Green chemistry will change the face of chemical industry and benefit future generations.
Up to now, most processes in the chemical industry were developed more than 20 years ago, and the processing costs at that time mainly included raw materials, energy consumption and labor costs. Due to the chemical industry to the atmosphere,
Water and soil release a lot of toxic and harmful substances. Take 1993 as an example, the United States only estimated the emissions of 365 toxic substances, and the emissions of the chemical industry were 3 billion pounds. Therefore, the treatment cost increases the waste control, treatment and burial. Environmental monitoring, compliance, accident liability compensation and other expenses. 1992, American chemical industry spent11500 million dollars on environmental protection and 700 billion dollars on cleaning up polluted areas. 1996 DuPont's total sales of chemicals in the United States is1800 million US dollars, and its environmental protection expenses are 10 billion US dollars. Therefore, from the requirements of environmental protection, economy and society. The chemical industry can no longer bear the cost of using and producing toxic and harmful substances. We must vigorously study and develop green chemistry to reduce and eliminate pollution from the source.
1990 The United States promulgated the Pollution Prevention Act. Establish pollution prevention as a national policy of the United States. The so-called pollution prevention means no more waste. There is no longer the problem of waste treatment, and green chemistry is the basis and important tool to realize pollution prevention and control. 1In April, 1995, American Vice President Al Gore announced the national environmental technology strategy. Its goal is: Earth Day in 2020. Waste is reduced by 40-50%, and raw materials consumed by each device are reduced by 20-25%. 1996 The United States established the Presidential Green Chemistry Challenge Award. These government actions have greatly promoted the vigorous development of green chemistry. In addition, Japan has also formulated a new sunshine plan. In the field of research and development of environmental technology. The contents of green chemistry such as environment-friendly manufacturing technology, environmental pollution reduction technology, carbon dioxide fixation and utilization technology are determined. In a word, the research of green chemistry has become an important research and development trend of foreign enterprises, governments and academic circles.
This is not only a severe challenge for our country, but also a rare development opportunity.