Chemistry

Chemistry

Chemistry, a branch of physical science, is the study of the composition, structure, properties and reaction of matter. Chemistry is the study of matter and energy and the relation between them. It is also the definition for physics. Chemistry and physics are main branches of physical science. In chemistry we study properties of substances and the interactions between different types of matter, particularly reactions that involve electrons. Physics is focused more on the nuclear part of the atom and the subatomic realm. In fact, they are two sides of the same coin.
Chemistry as science :
Sir Francis Bacon and chemists at Oxford, Robert Boyle,Robert Hooke and John Mayow began to reshape the old alchemical traditions into a scientific discipline. Boyle in particular is said as the founding father of chemistry due to his most important work, the classic chemistry text The Sceptical Chymist in which the differentiation is made between t alchemy and the empirical scientific discoveries of the new chemistry
Many important discoveries had been made, specifically relating to the n 'air' which was discovered to be composed of many different gases. The Scottish chemist Joseph Black and the Dutchman J. B. van Helmontdiscovered carbon dioxide, or what Black called 'fixed air' in 1754; Henry Cavendish discovered hydrogen and described its properties andJoseph Priestley and, independently, Carl Wilhelm Scheele isolated oxygen. John Dalton proposed the modern theory of atoms.That all substances are made of indivisible 'atoms' of matter . The development of the electrochemical theory of chemical combinations took place in the early 19th century due efforts of two scientists J. J. Berzelius and Humphry Davy, made possible by the prior invention of the voltaic pile by Alessandro Volta. Davy discovered nine new elements in which alkali metals William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an multiple of the atomic weight of hydrogen. J. A. R. Newlands made table of elements, which was then developed into the modern periodic table of elements by the German Julius Lothar Meyer and the Russian Dmitri Mendeleev in the The inert gases, later called the noble gases were discovered by William Ramsay with Lord Rayleigh at the end of the century, filling in the basic structure of the table.
chemical structure: In twentieth century the theoretical underpinnings of chemistry were finally understood due to remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897, J. J. Thomson of Cambridge Universitydiscovered the electron and soon the French scientist Becquerel as well as the couple Pierre and Marie Curie investigated the of radioactivity. In pioneering scattering experiments Ernest Rutherford at the University of Manchester discovered the internal structure of the atom and the existence of the proton, explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles. His work on atomic structure was improved on by his students, Niels Bohr and Henry Moseley. The electronic theory ofchemical bonds and molecular orbitals was developeD by the American scientists Linus Pauling and Gilbert N. Lewis. 2011 was declared by the United Nations as the International Year of Chemistry. It was an initiative of the International Union of Pure , Applied Chemistry, and of the United Nations Educational, Scientific, and Cultural Organization and involves chemical societies, academics, and institutions worldwide and relied on individual initiatives to make local and regional activities.
some important chemical pics give below

Element

Element Standard form of the periodic table of chemical elements. A chemical element is a substance which is made of a single type of atom, characterized by its particular number of protons in the nucleus 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 but they may not necessarily have the same mass number.Atoms of an element which have different mass numbers are known as isotopes.


Atom
based on the Rutherford model It consists of a core called the atomic nucleus surrounded by a space called the electron cloud. The nucleus is made up of positively charged protons and uncharged neutrons, while the electron cloud consists of negatively-charged electrons which orbit around the nucleus. In a neutral atom, the negatively-charged electrons balance out the positive charge of the protons. The nucleus is dense.The mass of a nucleon is 1,836 times that of an electron, butt the radius of an atom is about 10,000 times that of its nucleus. The atom is also the smallest entity that can be envisaged to show the chemical properties of the element, such as electronegativity, ionization potential, oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent)..

Chemical compound :

A compound is a pure chemical substance made of more than one element. The properties of a compound bear little similarity to its elements.] The standard nomenclature of compounds is set by the International Union of Pure and Applied Chemistry (IUPAC). Organic compoundsare named according to the organic nomenclature system. Inorganic compounds are named according to the inorganic nomenclature system. In addition the Chemical Abstracts Service has devised a method to index chemical substances. In this scheme each chemical substance is identifiable by a number known as its CAS registry number.
the pics of chemical bond given below:



Molecule:

 A ball-and-stick representation of the caffeine molecule (C8H10N4O2). A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion or a polyatomic ion. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrometer. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry.