1. What is chemistry?

　 Chemistry is the science of matter at the atomic to molecular scale, dealing primarily with collections of atoms, such as molecules, crystals, and metals. Chemistry deals with the composition and statistical properties of such structures, as well as their transformations and interactions to become materials encountered in everyday life. Chemistry also deals with understanding the properties and interactions of individual atoms with the purpose of applying that knowledge at the macroscopic level. According to modern chemistry, the physical properties of materials are generally determined by their structure at the atomic scale, which is itself defined by interatomic forces.

　  Disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter; organic chemistry, the study of organic matter; biochemistry, the study of substances found in biological organisms; physical chemistry, the energy related studies of chemical systems at macro, molecular and submolecular scales; analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system.

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.

Chemistry is the study of interactions of chemical substances with one another and energy.

2. History of chemistry

1661 - The Sceptical Chymist, by Robert Boyle. Chemistry is born, by being defined distinct from alchemy.

3. Essence of chemistry

　  Chemical compound
　  Chemical formula
　  Chemical reaction
　  Chemical substance

4.Subdisciplines

　  Chemistry is typically divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry.

　  Analytical chemistry is the analysis of material samples to gain an understanding of their chemical composition and structure. Analytical chemistry incorporates standardized experimental methods in chemistry. These methods may be used in all subdisciplines of chemistry, excluding purely theoretical chemistry.
　  Biochemistry is the study of the chemicals, chemical reactions and chemical interactions that take place in living organisms. Biochemistry and organic chemistry are closely related, as in medicinal chemistry or neurochemistry. Biochemistry is also associated with molecular biology and genetics. 
　 Inorganic chemistry is the study of the properties and reactions of inorganic compounds. The distinction between organic and inorganic disciplines is not absolute and there is much overlap, most importantly in the sub-discipline of organometallic chemistry.
　 Materials chemistry is the preparation, characterization, and understanding of substances with a useful function. The field is a new breadth of study in graduate programs, and it integrates elements from all classical areas of chemistry with a focus on fundamental issues that are unique to materials. Primary systems of study include the chemistry of condensed phases (solids, liquids, polymers) and interfaces between different phases. 
　 Neurochemistry is the study of neurochemicals; including transmitters, peptides, proteins, lipids, sugars, and nucleic acids; their interactions, and the roles they play in forming, maintaining, and modifying the nervous system.
　  Nuclear chemistry is the study of how subatomic particles come together and make nuclei. Modern Transmutation is a large component of nuclear chemistry, and the table of nuclides is an important result and tool for this field.　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Chemical basis of love, one of many applications of biochemistry.
　 Organic chemistry is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. An organic compound is defined as any compound based on a carbon skeleton. 
　 Physical chemistry is the study of the physical and fundamental basis of chemical systems and processes. In particular, the energetics and dynamics of such systems and processes are of interest to physical chemists. Important areas of study include chemical thermodynamics, chemical kinetics, electrochemistry, statistical mechanics, and spectroscopy. Physical chemistry has large overlap with molecular physics. Physical chemistry involves the use of infinitesimal calculus in deriving equations. It is usually associated with quantum chemistry and theoretical chemistry. Physical chemistry is a distinct discipline from chemical physics. 
　 Theoretical chemistry is the study of chemistry via fundamental theoretical reasoning (usually within mathematics or physics). In particular the application of quantum mechanics to chemistry is called quantum chemistry. Since the end of the Second World War, the development of computers has allowed a systematic development of computational chemistry, which is the art of developing and applying computer programs for solving chemical problems. Theoretical chemistry has large overlap with (theoretical and experimental) condensed matter physics and molecular physics.
　  Other fields include agrochemistry, astrochemistry, atmospheric chemistry, chemical engineering, chemical biology, chemo-informatics, electrochemistry, environmental chemistry, femtochemistry, flavor chemistry, flow chemistry, geochemistry, green chemistry, histochemistry, history of chemistry, hydrogenation chemistry, immunochemistry, marine chemistry, materials science, mathematical chemistry, mechanochemistry, medicinal chemistry, molecular biology, molecular mechanics, nanotechnology, natural product chemistry, oenology, neurochemistry, organometallic chemistry, petrochemistry, pharmacology, photochemistry, physical organic chemistry, phytochemistry, polymer chemistry, radiochemistry, solid-state chemistry, sonochemistry, supramolecular chemistry, surface chemistry, synthetic chemistry, thermochemistry, and many others.
5.Standard periodic table of the chemical elements

This common arrangement of the periodic table separates the lanthanoids and actinoids from other elements. The wide periodic table incorporates the f-block. The extended periodic table adds the 8th and 9th periods, incorporating the f-block and adding the theoretical g-block.

6. Chemical industry

　  The chemical industry represents an important economic activity. The global top 50 chemical producers in 2004 had sales of 587 billion US dollars with a profit margin of 8.1% and research and development spending of 2.1% of total chemical sales.

7.Some famous chemists

8. Professional societies

　  American Chemical Society
　 American Society for Neurochemistry
　  Chemical Institute of Canada
　  Chemical Society of Peru
　  International Union of Pure and Applied Chemistry
　  Royal Australian Chemical Institute
　  Royal Netherlands Chemical Society
　  Royal Society of Chemistry
　  Society of Chemical Industry
　  World Association of Theoretical and Computational Chemists

References:

[1]The Canadian Encyclopedia: Chemistry Subdisciplines

[2]The Canadian Encyclopedia: Chemistry Subdisciplines"Top 50 Chemical Producers". Chemical & Engineering News 83 (29): 20–23. July 18, 2005. 

Further reading

Popular reading
　  Atkins, P.W. Galileo's Finger (Oxford University Press) ISBN 0198609418
　  Atkins, P.W. Atkins' Molecules (Cambridge University Press) ISBN 0521823978
　  Stwertka, A. A Guide to the Elements (Oxford University Press) ISBN 0195150279
Introductory undergraduate text books
　  Atkins, P.W., Overton, T., Rourke, J., Weller, M. and Armstrong, F. Shriver and Atkins inorganic chemistry (4th edition) 2006 (Oxford University Press) ISBN 0-19-926463-5
　  Chang, Raymond. Chemistry 6th ed. Boston: James M. Smith, 1998. ISBN 0-07-115221-0.
　  J. P. Clayden, N. Greeves, S. G. Warren, P. D. Wothers (2000), Organic Chemistry (1st ed.), Oxford: Oxford University Press, ISBN 978-0-19-850346-0 
　  Voet and Voet Biochemistry (Wiley) ISBN 0-471-58651-X
Advanced undergraduate-level or graduate text books
　  Atkins, P.W. Physical Chemistry (Oxford University Press) ISBN 0-19-879285-9 
　  Atkins, P.W. et al. Molecular Quantum Mechanics (Oxford University Press)
　  McWeeny, R. Coulson's Valence (Oxford Science Publications) ISBN 0-19-855144-4
　  Pauling, L. The Nature of the chemical bond (Cornell University Press) ISBN 0-8014-0333-2
　  Pauling, L., and Wilson, E. B. Introduction to Quantum Mechanics with Applications to Chemistry (Dover Publications) ISBN 0-486-64871-0
　  Smart and Moore Solid State Chemistry: An Introduction (Chapman and Hall) ISBN 0-412-40040-5
　  Stephenson, G. Mathematical Methods for Science Students (Longman) ISBN 0-582-44416-0

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