Chemistry, PRO-SCH

How do you use raw plant materials to manufacture a best-selling perfume? How do you engineer household products that are compliant with environmentally-oriented guidelines? The answers to these questions require an understanding of the laws of chemistry, the science that deals with the properties, composition, and structure of elements and compounds, as well as the transformations that such substances undergo and the energy that is released or absorbed during those processes. Chemistry is also concerned with the utilization of natural substances and the creation of artificial ones. Over time, more than 8,000,000 different chemical substances, both natural and artificial, have been characterized and produced. Chemistry's vast scope comprises organic, inorganic, physical, analytical, and industrial chemistry, along with biochemistry, environmental chemistry, medicinal chemistry, and much more. Through the dedicated efforts of people such as Robert Boyle, Dmitri Mendeleev, John Dalton, Marie Curie, and Rosalind Franklin, the field of chemistry has led to exciting innovations as well as crucial advances in our understanding of how the world functions, starting with the miniscule and unassuming atom.
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Chemistry Encyclopedia Articles By Title

Prout, William
William Prout was an English chemist and biochemist noted for his discoveries concerning digestion, metabolic chemistry,......
psilocin
psilocin, hallucinogenic principle contained in any of various psilocybin mushrooms, notably the two Mexican species......
psilocybin
psilocybin, hallucinogenic principle that occurs in any of various psilocybin mushrooms, including the two Mexican......
purine
purine, any of a class of organic compounds of the heterocyclic series characterized by a two-ringed structure......
PVC
PVC, a synthetic resin made from the polymerization of vinyl chloride. Second only to polyethylene among the plastics......
pyran
pyran, any of a class of organic compounds of the heterocyclic series in which five carbon atoms and one oxygen......
pyrazine
pyrazine, any of a class of organic compounds of the heterocyclic series characterized by a ring structure containing......
pyrazole
pyrazole, any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed......
pyridine
pyridine, any of a class of organic compounds of the aromatic heterocyclic series characterized by a six-membered......
pyrimidine
pyrimidine, any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed......
pyrogallol
pyrogallol, an organic compound belonging to the phenol family, used as a photographic film developer and in the......
pyrolysis
pyrolysis, the chemical decomposition of organic (carbon-based) materials through the application of heat. Pyrolysis,......
pyrrole
pyrrole, any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed......
pyruvic acid
pyruvic acid, (CH3COCOOH), is an organic acid that probably occurs in all living cells. It ionizes to give a hydrogen......
quicklime
quicklime (CaO), compound of one atom of calcium and one atom of oxygen that is a white or grayish white solid......
quinidine
quinidine, drug used in the treatment of abnormal heart rhythms (arrhythmia) and malaria. Obtained from the bark......
quinine
quinine, drug obtained from cinchona bark that is used chiefly in the treatment of malaria, an infection caused......
quinoline
quinoline, any of a class of organic compounds of the aromatic heterocyclic series characterized by a double-ring......
quinone
quinone, any member of a class of cyclic organic compounds containing two carbonyl groups, > C = O, either adjacent......
radical
radical, in chemistry, molecule that contains at least one unpaired electron. Most molecules contain even numbers......
radioactive isotope
radioactive isotope, any of several species of the same chemical element with different masses whose nuclei are......
radium
radium (Ra), radioactive chemical element, the heaviest of the alkaline-earth metals of Group 2 (IIa) of the periodic......
radon
radon (Rn), chemical element, a heavy radioactive gas of Group 18 (noble gases) of the periodic table, generated......
Ramakrishnan, Venki
Venki Ramakrishnan is an Indian-born physicist and molecular biologist who was awarded the 2009 Nobel Prize for......
Ramsay, Sir William
Sir William Ramsay was a British physical chemist who discovered four gases (neon, argon, krypton, xenon) and showed......
rancidity
rancidity, condition produced by aerial oxidation of unsaturated fat present in foods and other products, marked......
Raoult, François-Marie
François-Marie Raoult was a French chemist who formulated a law on solutions (called Raoult’s law) that made it......
rayon
rayon, artificial textile material composed of regenerated and purified cellulose derived from plant sources. Developed......
reaction rate
reaction rate, in chemistry, the speed at which a chemical reaction proceeds. It is often expressed in terms of......
reaction, heat of
heat of reaction, the amount of heat that must be added or removed during a chemical reaction in order to keep......
reactor
reactor, in chemical engineering, device or vessel within which chemical processes are carried out for experimental......
reduction
reduction, any of a class of chemical reactions in which the number of electrons associated with an atom or a group......
Regnault, Henri-Victor
Henri-Victor Regnault was a French chemist and physicist noted for his work on the properties of gases. After studying......
Reichstein, Tadeus
Tadeus Reichstein was a Swiss chemist who, with Philip S. Hench and Edward C. Kendall, received the Nobel Prize......
relaxation phenomenon
relaxation phenomenon, in physics and chemistry, an effect related to the delay between the application of an external......
Relaxin
Relaxin, in common usage, the two-chain peptide hormone H2 relaxin, which belongs to the relaxin peptide family......
Remsen, Ira
Ira Remsen was an American chemist and university president, codiscoverer of saccharin. After studying at Columbia......
Renin
Renin, enzyme secreted by the kidney (and also, possibly, by the placenta) that is part of a physiological system......
renin-angiotensin system
renin-angiotensin system, physiological system that regulates blood pressure. Renin is an enzyme secreted into......
Rennin
Rennin, protein-digesting enzyme that curdles milk by transforming caseinogen into insoluble casein; it is found......
Repression
Repression, in metabolism, a control mechanism in which a protein molecule, called a repressor, prevents the synthesis......
reserpine
reserpine, drug derived from the roots of certain species of the tropical plant Rauwolfia. The powdered whole root......
resin
resin, any natural or synthetic organic compound consisting of a noncrystalline or viscous liquid substance. Natural......
resonance, theory of
theory of resonance, in chemistry, theory by which the actual normal state of a molecule is represented not by......
resorcinol
resorcinol, phenolic compound used in the manufacture of resins, plastics, dyes, medicine, and numerous other organic......
Restriction enzyme
Restriction enzyme, a protein produced by bacteria that cleaves DNA at specific sites along the molecule. In the......
Reverse transcriptase
Reverse transcriptase, an enzyme encoded from the genetic material of retroviruses that catalyzes the transcription......
rhenium
rhenium (Re), chemical element, a very rare metal of Group 7 (VIIb) of the periodic table and one of the densest......
rhodium
rhodium (Rh), chemical element, one of the platinum metals of Groups 8–10 (VIIIb), Periods 5 and 6, of the periodic......
Rhodopsin
Rhodopsin, pigment-containing sensory protein that converts light into an electrical signal. Rhodopsin is found......
riboflavin
riboflavin, a yellow, water-soluble organic compound that occurs abundantly in whey (the watery part of milk) and......
Ribose
Ribose, five-carbon sugar found in RNA (ribonucleic acid), where it alternates with phosphate groups to form the......
ribosomal RNA
ribosomal RNA (rRNA), molecule in cells that forms part of the protein-synthesizing organelle known as a ribosome......
Richards, Ellen Swallow
Ellen Swallow Richards was an American chemist and founder of the home economics movement in the United States.......
Richards, Theodore William
Theodore William Richards was an American chemist whose accurate determination of the atomic weights of approximately......
ricin
ricin, toxic protein (toxalbumin) occurring in the beanlike seeds of the castor-oil plant (Ricinus communis). Ricin,......
RNA
RNA, complex compound of high molecular weight that functions in cellular protein synthesis and replaces DNA (deoxyribonucleic......
Robinson, Sir Robert
Sir Robert Robinson was a British chemist, recipient of the Nobel Prize for Chemistry in 1947 for his research......
Robson, Richard
Richard Robson is an English-born Australian chemist who was awarded the 2025 Nobel Prize for Chemistry for his......
Rochelle salt
Rochelle salt, a crystalline solid having a large piezoelectric effect (electric charge induced on its surfaces......
Rodbell, Martin
Martin Rodbell was an American biochemist who was awarded the 1994 Nobel Prize for Physiology or Medicine for his......
Roebuck, John
John Roebuck was a British physician, chemist, and inventor, perhaps best-known for having subsidized the experiments......
roentgenium
roentgenium (Rg), artificially produced transuranium element of atomic number 111. In 1994 scientists at the Institute......
Rose family
Rose family, a distinguished family of German chemists. Valentine Rose, the elder (b. Aug. 16, 1736, Neuruppin,......
Rose, Irwin
Irwin Rose was an American biochemist who shared the 2004 Nobel Prize for Chemistry with Aaron J. Ciechanover and......
Rothman, James E.
James E. Rothman is an American biochemist and cell biologist who discovered the molecular machinery involved in......
Rowland, F. Sherwood
F. Sherwood Rowland was an American chemist who shared the 1995 Nobel Prize for Chemistry with chemists Mario Molina......
Royal Swedish Academy of Sciences
Royal Swedish Academy of Sciences, independent nongovernmental organization headquartered in Stockholm and primarily......
rubidium
rubidium (Rb), chemical element of Group 1 (Ia) in the periodic table, the alkali metal group. Rubidium is the......
Runge, Friedlieb Ferdinand
Friedlieb Ferdinand Runge was a German chemist considered to be the originator of the widely used analytic technique......
Rush, Benjamin
Benjamin Rush was an American physician and political leader, a member of the Continental Congress and a signer......
ruthenium
ruthenium (Ru), chemical element, one of the platinum metals of Groups 8–10 (VIIIb), Periods 5 and 6, of the periodic......
Rutherford, Ernest
Ernest Rutherford was a New Zealand-born British physicist considered the greatest experimentalist since Michael......
rutherfordium
rutherfordium (Rf), an artificially produced radioactive transuranium element in Group IVb of the periodic table,......
Ružička, Leopold
Leopold Ružička was a Swiss chemist and joint recipient, with Adolf Butenandt of Germany, of the 1939 Nobel Prize......
Sabatier, Paul
Paul Sabatier was a French organic chemist and corecipient, with Victor Grignard, of the 1912 Nobel Prize for Chemistry......
saccharin
saccharin, organic compound employed as a non-nutritive sweetening agent. It occurs as insoluble saccharin or in......
sago
sago, food starch prepared from carbohydrate material stored in the trunks of several palms, the main source being......
Sainte-Claire Deville, Henri-Étienne
Henri-Étienne Sainte-Claire Deville was a French chemical researcher who invented the first economical process......
salicylic acid
salicylic acid, a white, crystalline solid that is used chiefly in the preparation of aspirin and other pharmaceutical......
salinity
salinity, the amount of dissolved salts present in water. In natural bodies of water, salinity is most commonly......
salt
salt (NaCl), mineral substance of great importance to human and animal health, as well as to industry. The mineral......
salt
salt, in chemistry, substance produced by the reaction of an acid with a base. A salt consists of the positive......
saltpetre
saltpetre, any of three naturally occurring nitrates, distinguished as (1) ordinary saltpetre, or potassium nitrate,......
samarium
samarium (Sm), chemical element, a rare-earth metal of the lanthanide series of the periodic table. Samarium is......
Samuelsson, Bengt Ingemar
Bengt Ingemar Samuelsson was a Swedish biochemist who was a corecipient, with fellow Swede Sune K. Bergström and......
Sancar, Aziz
Aziz Sancar is a Turkish-American biochemist who contributed to mechanistic discoveries underlying a cellular process......
Sanger, Frederick
Frederick Sanger was an English biochemist who was twice the recipient of the Nobel Prize for Chemistry. He was......
Sapogenin
Sapogenin, any of a class of organic compounds occurring in many species of plants as derivatives of the steroid......
Saponin
Saponin, any of numerous substances, occurring in plants, that form stable foams with water, including the constituents......
saturated fat
saturated fat, a fatty acid in which the hydrocarbon molecules have a hydrogen atom on every carbon and thus are......
Saussure, Nicolas-Théodore de
Nicolas-Théodore de Saussure was a Swiss chemist and plant physiologist whose quantitative experiments on the influence......
Sauvage, Jean-Pierre
Jean-Pierre Sauvage is a French chemist who was awarded the 2016 Nobel Prize in Chemistry for his work on molecular......
scandium
scandium (Sc), chemical element, a rare-earth metal of Group 3 of the periodic table. Scandium is a silvery white,......
Schaefer, Vincent Joseph
Vincent Joseph Schaefer was an American research chemist and meteorologist who in 1946 carried out the first systematic......
Scheele, Carl Wilhelm
Carl Wilhelm Scheele was a German Swedish chemist who independently discovered oxygen, chlorine, and manganese.......

Chemistry Encyclopedia Articles By Title