Organic Chemistry
The history of chemistry spans a period from very old times to the present.Since several millennia BC,civilization were using technologies that would eventually form the basis of the various branches of chemistry.Examples include extracting metals from ores,making pottery and glazes,fermenting beer and wine,extracting chemicals from plants for medicine and perfume,rendering fat into soap,making glass,and making alloys like bronze.Chemistry was peceded by its protoscience,alchemy,which is an intuitive but non-scientific approach to understanding the constituents of matter and their interactions.
A chemical element is a pure substance which is composed of a single type of atom,characterized by its particular number of protons in the nuclei of its atoms,known as the atomic number and represented by the symbol Z.The mass number is the sum of the number of protons and neutrons in a nucleus.Although all the nuclei of all atoms belonging to one element will have the same atomic number,they may not necessarily have the same mass number,atoms of an element which have different mass numbers are known as isotopes,For example,all atoms with 6 protons in their nuclei are atoms of the chemical element carbon,but atoms of carbon may have mass numbers of 12 or 13.
The standard presentation of the chemical elements is in the periodic table,which orders elements by atomic number.The periodic table is arranged in groups,or columns,and periods,or rows.The periodic table is useful in identifying periodic trends.
A chemical element is a pure substance which is composed of a single type of atom,characterized by its particular number of protons in the nuclei of its atoms,known as the atomic number and represented by the symbol Z.The mass number is the sum of the number of protons and neutrons in a nucleus.Although all the nuclei of all atoms belonging to one element will have the same atomic number,they may not necessarily have the same mass number,atoms of an element which have different mass numbers are known as isotopes,For example,all atoms with 6 protons in their nuclei are atoms of the chemical element carbon,but atoms of carbon may have mass numbers of 12 or 13.
The standard presentation of the chemical elements is in the periodic table,which orders elements by atomic number.The periodic table is arranged in groups,or columns,and periods,or rows.The periodic table is useful in identifying periodic trends.
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