Kidney Dialysis A hospital patient whose kidneys have ceased to function receives dialysis. In this process, the patient’s blood is pumped through a dialysis machine, where it is filtered to remove waste products, then returned to the patient’s body through a vein.Bruce Coleman, Inc./SUI Medical School
For a large part of recorded history, science had little bearing on people's everyday lives. Scientific knowledge was gathered for its own sake, and it had few practical applications. However, with the dawn of the Industrial Revolution in the 18th century, this rapidly changed. Today, science has a profound effect on the way we live, largely through technology—the use of scientific knowledge for practical purposes.
Some forms of technology have become so well established that it is easy to forget the great scientific achievements that they represent. The refrigerator, for example, owes its existence to a discovery that liquids take in energy when they evaporate, a phenomenon known as latent heat. The principle of latent heat was first exploited in a practical way in 1876, and the refrigerator has played a major role in maintaining public health ever since (see Refrigeration). The first automobile, dating from the 1880s, made use of many advances in physics and engineering, including reliable ways of generating high-voltage sparks, while the first computers emerged in the 1940s from simultaneous advances in electronics and mathematics.
Saturday, September 4, 2010
Technology
Technology, general term for the processes by which human beings fashion tools and machines to increase their control and understanding of the material environment. The term is derived from the Greek words tekhnē, which refers to an art or craft, and logia, meaning an area of study; thus, technology means, literally, the study, or science, of crafting.
Many historians of science argue not only that technology is an essential condition of advanced, industrial civilization but also that the rate of technological change has developed its own momentum in recent centuries. Innovations now seem to appear at a rate that increases geometrically, without respect to geographical limits or political systems. These innovations tend to transform traditional cultural systems, frequently with unexpected social consequences. Thus technology can be conceived as both a creative and a destructive process.
Many historians of science argue not only that technology is an essential condition of advanced, industrial civilization but also that the rate of technological change has developed its own momentum in recent centuries. Innovations now seem to appear at a rate that increases geometrically, without respect to geographical limits or political systems. These innovations tend to transform traditional cultural systems, frequently with unexpected social consequences. Thus technology can be conceived as both a creative and a destructive process.
science and technology
The meanings of the terms science and technology have changed significantly from one generation to another. More similarities than differences, however, can be found between the terms.
Both science and technology imply a thinking process, both are concerned with causal relationships in the material world, and both employ an experimental methodology that results in empirical demonstrations that can be verified by repetition (see Scientific Method). Science, at least in theory, is less concerned with the practicality of its results and more concerned with the development of general laws, but in practice science and technology are inextricably involved with each other. The varying interplay of the two can be observed in the historical development of such practitioners as chemists, engineers, physicists, astronomers, carpenters, potters, and many other specialists. Differing educational requirements, social status, vocabulary, methodology, and types of rewards, as well as institutional objectives and professional goals, contribute to such distinctions as can be made between the activities of scientists and technologists; but throughout history the practitioners of “pure” science have made many practical as well as theoretical contributions.
Both science and technology imply a thinking process, both are concerned with causal relationships in the material world, and both employ an experimental methodology that results in empirical demonstrations that can be verified by repetition (see Scientific Method). Science, at least in theory, is less concerned with the practicality of its results and more concerned with the development of general laws, but in practice science and technology are inextricably involved with each other. The varying interplay of the two can be observed in the historical development of such practitioners as chemists, engineers, physicists, astronomers, carpenters, potters, and many other specialists. Differing educational requirements, social status, vocabulary, methodology, and types of rewards, as well as institutional objectives and professional goals, contribute to such distinctions as can be made between the activities of scientists and technologists; but throughout history the practitioners of “pure” science have made many practical as well as theoretical contributions.
Nuclear Energy
Nuclear Energy, energy released during the splitting or fusing of atomic nuclei. The energy of any system, whether physical, chemical, or nuclear, is manifested by the system’s ability to do work or to release heat or radiation. The total energy in a system is always conserved, but it can be transferred to another system or changed in form.
The first large-scale nuclear reactors were built in 1944 at Hanford, Washington, for the production of nuclear weapons material. The fuel was natural uranium metal; the moderator, graphite. Plutonium was produced in these plants by neutron absorption in uranium-238; the power produced was not used.
If fusion energy does become practical, it offers the following advantages: (1) a limitless source of fuel, deuterium from the ocean; (2) no possibility of a reactor accident, as the amount of fuel in the system is very small; and (3) waste products much less radioactive and simpler to handle than those from fission systems.
The first large-scale nuclear reactors were built in 1944 at Hanford, Washington, for the production of nuclear weapons material. The fuel was natural uranium metal; the moderator, graphite. Plutonium was produced in these plants by neutron absorption in uranium-238; the power produced was not used.
If fusion energy does become practical, it offers the following advantages: (1) a limitless source of fuel, deuterium from the ocean; (2) no possibility of a reactor accident, as the amount of fuel in the system is very small; and (3) waste products much less radioactive and simpler to handle than those from fission systems.
Science
Science, systematic study of anything that can be examined, tested, and verified. The word science is derived from the Latin word scire, meaning “to know.” From its early beginnings, science has developed into one of the greatest and most influential fields of human endeavor. Today different branches of science investigate almost everything that can be observed or detected, and science as a whole shapes the way we understand the universe, our planet, ourselves, and other living things.
Science develops through objective analysis, instead of through personal belief. Knowledge gained in science accumulates as time goes by, building on work performed earlier. Some of this knowledge—such as our understanding of numbers—stretches back to the time of ancient civilizations, when scientific thought first began. Other scientific knowledge—such as our understanding of genes that cause cancer or of quarks (the smallest known building block of matter)—dates back less than 50 years. However, in all fields of science, old or new, researchers use the same systematic approach, known as the scientific method, to add to what is known.
Science develops through objective analysis, instead of through personal belief. Knowledge gained in science accumulates as time goes by, building on work performed earlier. Some of this knowledge—such as our understanding of numbers—stretches back to the time of ancient civilizations, when scientific thought first began. Other scientific knowledge—such as our understanding of genes that cause cancer or of quarks (the smallest known building block of matter)—dates back less than 50 years. However, in all fields of science, old or new, researchers use the same systematic approach, known as the scientific method, to add to what is known.
HISTORY OF SCIENCE
Science exists because humans have a natural curiosity and an ability to organize and record things. Curiosity is a characteristic shown by many other animals, but organizing and recording knowledge is a skill demonstrated by humans alone.
During prehistoric times, humans recorded information in a rudimentary way. They made paintings on the walls of caves, and they also carved numerical records on bones or stones. They may also have used other ways of recording numerical figures, such as making knots in leather cords, but because these records were perishable, no traces of them remain. But with the invention of writing about 6,000 years ago, a new and much more flexible system of recording knowledge appeared.
During prehistoric times, humans recorded information in a rudimentary way. They made paintings on the walls of caves, and they also carved numerical records on bones or stones. They may also have used other ways of recording numerical figures, such as making knots in leather cords, but because these records were perishable, no traces of them remain. But with the invention of writing about 6,000 years ago, a new and much more flexible system of recording knowledge appeared.
elements of the periodic table
Atomic Number Name Symbol Atomic Weight Group Date Discovered Discovered By
1 Hydrogen H 1.0079 Nonmetals 1766 Henry Cavendish
2 Helium He 4.0026 Noble gases 1868 Pierre Janssen
3 Lithium Li 6.941 Alkali metals 1817 Johan Arfwedson
4 Beryllium Be 9.0122 Alkaline earth metals 1798 Louis-Nicolas Vauquelin (isolated by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy 1828)
5 Boron B 10.81 Nonmetals 1808 Humphry Davy, and independently by Joseph Gay-Lussac and Louis-Jacques Thénard
6 Carbon C 12.011 Nonmetals prehistoric unknown
7 Nitrogen N 14.0067 Nonmetals 1772 Daniel Rutherford
8 Oxygen O 15.9994 Nonmetals 1774 Joseph Priestley and Karl Scheele, independently of each other
9 Fluorine F 18.9984 Halogens 1771 Karl Scheele (isolated by Henri Moissan 1886)
10 Neon Ne 20.1798 Noble gases 1898 William Ramsay and Morris Travers
11 Sodium Na 22.9898 Alkali metals 1807 Humphry Davy
12 Magnesium Mg 24.3051 Alkaline earth metals 1755 Joseph Black (oxide isolated by Humphry Davy 1808; pure form isolated by Antoine-Alexandre-Brutus Bussy 1828)
13 Aluminum Al 26.9815 Other metals 1824 Hans Oersted (also attributed to Friedrich Wöhler 1827)
14 Silicon Si 28.0855 Nonmetals 1823 Johan Arfwedson
15 Phosphorus P 30.9738 Nonmetals 1674 Hennig Brand
16 Sulfur S 32.067 Nonmetals prehistoric unknown
17 Chlorine Cl 35.4528 Halogens 1774 Karl Scheele
18 Argon Ar 39.948 Noble gases 1894 John Rayleigh and William Ramsay
19 Potassium K 39.0983 Alkali metals 1807 Humphry Davy
20 Calcium Ca 40.078 Alkaline earth metals 1808 Humphry Davy
21 Scandium Sc 44.9559 Transition metals 1876 Lars Nilson
22 Titanium Ti 47.867 Transition metals 1790 William Gregor
23 Vanadium V 50.9415 Transition metals 1801 Andrés del Rio (disputed), or Nils Sefström 1830
24 Chromium Cr 51.9962 Transition metals 1797 Louis-Nicolas Vauquelin
25 Manganese Mn 54.938 Transition metals 1774 Johann Gottlieb Gahn
26 Iron Fe 55.845 Transition metals prehistoric unknown
27 Cobalt Co 58.9332 Transition metals 1730 Georg Brandt
28 Nickel Ni 58.6934 Transition metals 1751 Axel Cronstedt
29 Copper Cu 63.546 Transition metals prehistoric unknown
30 Zinc Zn 65.409 Transition metals prehistoric unknown
31 Gallium Ga 69.723 Other metals 1875 Paul Lecoq de Boisbaudran
32 Germanium Ge 72.61 Other metals 1886 Clemens Winkler
33 Arsenic As 74.9216 Nonmetals prehistoric unknown
34 Selenium Se 78.96 Nonmetals 1817 Jöns Berzelius
35 Bromine Br 79.904 Halogens 1826 Antoine-Jérôme Balard
36 Krypton Kr 83.798 Noble gases 1898 William Ramsay and Morris Travers
37 Rubidium Rb 85.4678 Alkali metals 1861 Robert Bunsen and Gustav Kirchhoff
38 Strontium Sr 87.62 Alkaline earth metals 1808 Humphry Davy
39 Yttrium Y 88.906 Transition metals 1794 Johan Gadolin
40 Zirconium Zr 91.224 Transition metals 1789 Martin Klaproth
41 Niobium Nb 92.9064 Transition metals 1801 Charles Hatchett
42 Molybdenum Mo 95.94 Transition metals 1781 named by Karl Scheele (isolated by Peter Jacob Hjelm 1782)
43 Technetium Tc (98) Transition metals 1937 Carlo Perrier and Emilio Segrè
44 Ruthenium Ru 101.07 Transition metals 1827 G. W. Osann (isolated by Karl Klaus 1844)
45 Rhodium Rh 102.9055 Transition metals 1804 William Wollaston
46 Palladium Pd 106.42 Transition metals 1804 William Wollaston
47 Silver Ag 107.8682 Transition metals prehistoric unknown
48 Cadmium Cd 112.412 Transition metals 1817 Friedrich Strohmeyer
49 Indium In 114.818 Other metals 1863 Ferdinand Reich and Hieronymus Richter
50 Tin Sn 118.711 Other metals prehistoric unknown
51 Antimony Sb 121.760 Other metals prehistoric unknown
52 Tellurium Te 127.60 Nonmetals 1782 Franz Müller
53 Iodine I 126.9045 Halogens 1811 Bernard Courtois
54 Xenon Xe 131.29 Noble gases 1898 William Ramsay and Morris Travers
55 Cesium Cs 132.9054 Alkali metals 1860 Robert Bunsen and Gustav Kirchhoff
56 Barium Ba 137.328 Alkaline earth metals 1808 Humphry Davy
57 Lanthanum La 138.9055 Lanthanide series 1839 Carl Mosander
58 Cerium Ce 140.115 Lanthanide series 1804 Jöns Berzelius and Wilhelm Hisinger, and independently by Martin Klaproth
59 Praseodymium Pr 140.908 Lanthanide series 1885 Carl von Welsbach
60 Neodymium Nd 144.24 Lanthanide series 1885 Carl von Welsbach
61 Promethium Pm (145) Lanthanide series 1945 J. A. Marinsky, Lawrence Glendenin, and Charles Coryell
62 Samarium Sm 150.36 Lanthanide series 1879 Paul Lecoq de Boisbaudran
63 Europium Eu 151.966 Lanthanide series 1901 Eugène Demarçay
64 Gadolinium Gd 157.25 Lanthanide series 1886 Paul Lecoq de Boisbaudran
65 Terbium Tb 158.9253 Lanthanide series 1843 Carl Mosander
66 Dysprosium Dy 162.500 Lanthanide series 1886 Paul Lecoq de Boisbaudran
67 Holmium Ho 164.9303 Lanthanide series 1879 Per Cleve
68 Erbium Er 167.26 Lanthanide series 1843 Carl Mosander
69 Thulium Tm 168.9342 Lanthanide series 1879 Per Cleve
70 Ytterbium Yb 173.04 Lanthanide series 1878 Jean Charles de Marignac
71 Lutetium Lu 174.967 Transition metals 1907 Georges Urbain and Carl von Welsbach, independently of each other
72 Hafnium Hf 178.49 Transition metals 1913 Dirk Coster and Georg von Hevesy
73 Tantalum Ta 180.948 Transition metals 1802 Anders Ekeberg
74 Tungsten W 183.84 Transition metals 1783 isolated by Juan José Elhuyar and Fausto Elhuyar
75 Rhenium Re 186.207 Transition metals 1925 Walter Noddack, Ida Tacke, and Otto Berg
76 Osmium Os 190.23 Transition metals 1804 Smithson Tennant
77 Iridium Ir 192.217 Transition metals 1804 Smithson Tennant
78 Platinum Pt 195.08 Transition metals 1557 Julius Scaliger
79 Gold Au 196.9665 Transition metals prehistoric unknown
80 Mercury Hg 200.59 Transition metals prehistoric unknown
81 Thallium Tl 204.3833 Other metals 1861 William Crookes (isolated by William Crookes and Claude August Lamy, independently of each other, in 1862)
82 Lead Pb 207.2 Other metals prehistoric unknown
83 Bismuth Bi 208.9804 Other metals prehistoric unknown
84 Polonium Po (209) Other metals 1898 Marie and Pierre Curie
85 Astatine At (210) Halogens 1940 Dale R. Corson, K. R. MacKenzie, and Emilio Segrè
86 Radon Rn (222) Noble gases 1900 Friedrich Dorn
87 Francium Fr (223) Alkali metals 1939 Marguérite Perey
88 Radium Ra (226) Alkaline earth metals 1898 Marie Curie
89 Actinium Ac (227) Actinide series 1899 André Debierne
90 Thorium Th 232.0381 Actinide series 1828 Jöns Berzelius
91 Protactinium Pa 231.036 Actinide series 1913 Kasimir Fajans and O. Göhring
92 Uranium U 238.0289 Actinide series 1789 Martin Klaproth (isolated by Eugène Péligot 1841)
93 Neptunium Np (237) Actinide series 1940 Edwin McMillan and Philip Abelson
94 Plutonium Pu (244) Actinide series 1940 Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl
95 Americium Am 243 Actinide series 1944 Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso
96 Curium Cm (247) Actinide series 1944 Glenn Seaborg, Ralph James, and Albert Ghiorso
97 Berkelium Bk (247) Actinide series 1949 Glenn Seaborg, Stanley Thompson, and Albert Ghiorso
98 Californium Cf (251) Actinide series 1950 Glenn Seaborg, Stanley Thompson, Kenneth Street, Jr., and Albert Ghiorso
99 Einsteinium Es (252) Actinide series 1952 Albert Ghiorso and coworkers
100 Fermium Fm (257) Actinide series 1955 Albert Ghiorso and coworkers
101 Mendelevium Md (258) Actinide series 1955 Albert Ghiorso, Bernard G. Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg
102 Nobelium No (259) Actinide series 1958 Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg
103 Lawrencium Lr (260) Transition metals 1961 Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert Latimer
104 Rutherfordium Rf (261) Transition metals 1969 claimed by U.S. scientist Albert Ghiorso and coworkers (disputed by Soviet workers)
105 Dubnium Db (262) Transition metals 1970 claimed by Albert Ghiorso and coworkers (disputed by Soviet workers)
106 Seaborgium Sg (266) Transition metals 1974 claimed by Georgii Flerov and coworkers, and independently by Albert Ghiorso and coworkers
107 Bohrium Bh (262) Transition metals 1976 Georgii Flerov and Yuri Oganessian (confirmed by German scientist Peter Armbruster and coworkers)
108 Hassium Hs (263) Transition metals 1984 Peter Armbruster and coworkers
109 Meitnerium Mt (268) Transition metals 1982 Peter Armbruster and coworkers
110 Darmstadtium Ds (271) Transition metals 1994 team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
111 Unununium Uuu (272) Transition metals 1994 team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
112 Ununbium Uub (277) Transition metals 1996 team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
114 Ununquadium Uuq (285) Other metals 1998 team at the Joint Institute for Nuclear Research, Dubna, Russia
116 Ununhexium Uuh (292) Other metals 2000 team at the Joint Institute for Nuclear Research, Dubna, Russia
1 Hydrogen H 1.0079 Nonmetals 1766 Henry Cavendish
2 Helium He 4.0026 Noble gases 1868 Pierre Janssen
3 Lithium Li 6.941 Alkali metals 1817 Johan Arfwedson
4 Beryllium Be 9.0122 Alkaline earth metals 1798 Louis-Nicolas Vauquelin (isolated by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy 1828)
5 Boron B 10.81 Nonmetals 1808 Humphry Davy, and independently by Joseph Gay-Lussac and Louis-Jacques Thénard
6 Carbon C 12.011 Nonmetals prehistoric unknown
7 Nitrogen N 14.0067 Nonmetals 1772 Daniel Rutherford
8 Oxygen O 15.9994 Nonmetals 1774 Joseph Priestley and Karl Scheele, independently of each other
9 Fluorine F 18.9984 Halogens 1771 Karl Scheele (isolated by Henri Moissan 1886)
10 Neon Ne 20.1798 Noble gases 1898 William Ramsay and Morris Travers
11 Sodium Na 22.9898 Alkali metals 1807 Humphry Davy
12 Magnesium Mg 24.3051 Alkaline earth metals 1755 Joseph Black (oxide isolated by Humphry Davy 1808; pure form isolated by Antoine-Alexandre-Brutus Bussy 1828)
13 Aluminum Al 26.9815 Other metals 1824 Hans Oersted (also attributed to Friedrich Wöhler 1827)
14 Silicon Si 28.0855 Nonmetals 1823 Johan Arfwedson
15 Phosphorus P 30.9738 Nonmetals 1674 Hennig Brand
16 Sulfur S 32.067 Nonmetals prehistoric unknown
17 Chlorine Cl 35.4528 Halogens 1774 Karl Scheele
18 Argon Ar 39.948 Noble gases 1894 John Rayleigh and William Ramsay
19 Potassium K 39.0983 Alkali metals 1807 Humphry Davy
20 Calcium Ca 40.078 Alkaline earth metals 1808 Humphry Davy
21 Scandium Sc 44.9559 Transition metals 1876 Lars Nilson
22 Titanium Ti 47.867 Transition metals 1790 William Gregor
23 Vanadium V 50.9415 Transition metals 1801 Andrés del Rio (disputed), or Nils Sefström 1830
24 Chromium Cr 51.9962 Transition metals 1797 Louis-Nicolas Vauquelin
25 Manganese Mn 54.938 Transition metals 1774 Johann Gottlieb Gahn
26 Iron Fe 55.845 Transition metals prehistoric unknown
27 Cobalt Co 58.9332 Transition metals 1730 Georg Brandt
28 Nickel Ni 58.6934 Transition metals 1751 Axel Cronstedt
29 Copper Cu 63.546 Transition metals prehistoric unknown
30 Zinc Zn 65.409 Transition metals prehistoric unknown
31 Gallium Ga 69.723 Other metals 1875 Paul Lecoq de Boisbaudran
32 Germanium Ge 72.61 Other metals 1886 Clemens Winkler
33 Arsenic As 74.9216 Nonmetals prehistoric unknown
34 Selenium Se 78.96 Nonmetals 1817 Jöns Berzelius
35 Bromine Br 79.904 Halogens 1826 Antoine-Jérôme Balard
36 Krypton Kr 83.798 Noble gases 1898 William Ramsay and Morris Travers
37 Rubidium Rb 85.4678 Alkali metals 1861 Robert Bunsen and Gustav Kirchhoff
38 Strontium Sr 87.62 Alkaline earth metals 1808 Humphry Davy
39 Yttrium Y 88.906 Transition metals 1794 Johan Gadolin
40 Zirconium Zr 91.224 Transition metals 1789 Martin Klaproth
41 Niobium Nb 92.9064 Transition metals 1801 Charles Hatchett
42 Molybdenum Mo 95.94 Transition metals 1781 named by Karl Scheele (isolated by Peter Jacob Hjelm 1782)
43 Technetium Tc (98) Transition metals 1937 Carlo Perrier and Emilio Segrè
44 Ruthenium Ru 101.07 Transition metals 1827 G. W. Osann (isolated by Karl Klaus 1844)
45 Rhodium Rh 102.9055 Transition metals 1804 William Wollaston
46 Palladium Pd 106.42 Transition metals 1804 William Wollaston
47 Silver Ag 107.8682 Transition metals prehistoric unknown
48 Cadmium Cd 112.412 Transition metals 1817 Friedrich Strohmeyer
49 Indium In 114.818 Other metals 1863 Ferdinand Reich and Hieronymus Richter
50 Tin Sn 118.711 Other metals prehistoric unknown
51 Antimony Sb 121.760 Other metals prehistoric unknown
52 Tellurium Te 127.60 Nonmetals 1782 Franz Müller
53 Iodine I 126.9045 Halogens 1811 Bernard Courtois
54 Xenon Xe 131.29 Noble gases 1898 William Ramsay and Morris Travers
55 Cesium Cs 132.9054 Alkali metals 1860 Robert Bunsen and Gustav Kirchhoff
56 Barium Ba 137.328 Alkaline earth metals 1808 Humphry Davy
57 Lanthanum La 138.9055 Lanthanide series 1839 Carl Mosander
58 Cerium Ce 140.115 Lanthanide series 1804 Jöns Berzelius and Wilhelm Hisinger, and independently by Martin Klaproth
59 Praseodymium Pr 140.908 Lanthanide series 1885 Carl von Welsbach
60 Neodymium Nd 144.24 Lanthanide series 1885 Carl von Welsbach
61 Promethium Pm (145) Lanthanide series 1945 J. A. Marinsky, Lawrence Glendenin, and Charles Coryell
62 Samarium Sm 150.36 Lanthanide series 1879 Paul Lecoq de Boisbaudran
63 Europium Eu 151.966 Lanthanide series 1901 Eugène Demarçay
64 Gadolinium Gd 157.25 Lanthanide series 1886 Paul Lecoq de Boisbaudran
65 Terbium Tb 158.9253 Lanthanide series 1843 Carl Mosander
66 Dysprosium Dy 162.500 Lanthanide series 1886 Paul Lecoq de Boisbaudran
67 Holmium Ho 164.9303 Lanthanide series 1879 Per Cleve
68 Erbium Er 167.26 Lanthanide series 1843 Carl Mosander
69 Thulium Tm 168.9342 Lanthanide series 1879 Per Cleve
70 Ytterbium Yb 173.04 Lanthanide series 1878 Jean Charles de Marignac
71 Lutetium Lu 174.967 Transition metals 1907 Georges Urbain and Carl von Welsbach, independently of each other
72 Hafnium Hf 178.49 Transition metals 1913 Dirk Coster and Georg von Hevesy
73 Tantalum Ta 180.948 Transition metals 1802 Anders Ekeberg
74 Tungsten W 183.84 Transition metals 1783 isolated by Juan José Elhuyar and Fausto Elhuyar
75 Rhenium Re 186.207 Transition metals 1925 Walter Noddack, Ida Tacke, and Otto Berg
76 Osmium Os 190.23 Transition metals 1804 Smithson Tennant
77 Iridium Ir 192.217 Transition metals 1804 Smithson Tennant
78 Platinum Pt 195.08 Transition metals 1557 Julius Scaliger
79 Gold Au 196.9665 Transition metals prehistoric unknown
80 Mercury Hg 200.59 Transition metals prehistoric unknown
81 Thallium Tl 204.3833 Other metals 1861 William Crookes (isolated by William Crookes and Claude August Lamy, independently of each other, in 1862)
82 Lead Pb 207.2 Other metals prehistoric unknown
83 Bismuth Bi 208.9804 Other metals prehistoric unknown
84 Polonium Po (209) Other metals 1898 Marie and Pierre Curie
85 Astatine At (210) Halogens 1940 Dale R. Corson, K. R. MacKenzie, and Emilio Segrè
86 Radon Rn (222) Noble gases 1900 Friedrich Dorn
87 Francium Fr (223) Alkali metals 1939 Marguérite Perey
88 Radium Ra (226) Alkaline earth metals 1898 Marie Curie
89 Actinium Ac (227) Actinide series 1899 André Debierne
90 Thorium Th 232.0381 Actinide series 1828 Jöns Berzelius
91 Protactinium Pa 231.036 Actinide series 1913 Kasimir Fajans and O. Göhring
92 Uranium U 238.0289 Actinide series 1789 Martin Klaproth (isolated by Eugène Péligot 1841)
93 Neptunium Np (237) Actinide series 1940 Edwin McMillan and Philip Abelson
94 Plutonium Pu (244) Actinide series 1940 Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl
95 Americium Am 243 Actinide series 1944 Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso
96 Curium Cm (247) Actinide series 1944 Glenn Seaborg, Ralph James, and Albert Ghiorso
97 Berkelium Bk (247) Actinide series 1949 Glenn Seaborg, Stanley Thompson, and Albert Ghiorso
98 Californium Cf (251) Actinide series 1950 Glenn Seaborg, Stanley Thompson, Kenneth Street, Jr., and Albert Ghiorso
99 Einsteinium Es (252) Actinide series 1952 Albert Ghiorso and coworkers
100 Fermium Fm (257) Actinide series 1955 Albert Ghiorso and coworkers
101 Mendelevium Md (258) Actinide series 1955 Albert Ghiorso, Bernard G. Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg
102 Nobelium No (259) Actinide series 1958 Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg
103 Lawrencium Lr (260) Transition metals 1961 Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert Latimer
104 Rutherfordium Rf (261) Transition metals 1969 claimed by U.S. scientist Albert Ghiorso and coworkers (disputed by Soviet workers)
105 Dubnium Db (262) Transition metals 1970 claimed by Albert Ghiorso and coworkers (disputed by Soviet workers)
106 Seaborgium Sg (266) Transition metals 1974 claimed by Georgii Flerov and coworkers, and independently by Albert Ghiorso and coworkers
107 Bohrium Bh (262) Transition metals 1976 Georgii Flerov and Yuri Oganessian (confirmed by German scientist Peter Armbruster and coworkers)
108 Hassium Hs (263) Transition metals 1984 Peter Armbruster and coworkers
109 Meitnerium Mt (268) Transition metals 1982 Peter Armbruster and coworkers
110 Darmstadtium Ds (271) Transition metals 1994 team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
111 Unununium Uuu (272) Transition metals 1994 team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
112 Ununbium Uub (277) Transition metals 1996 team at the Heavy-Ion Research Laboratory, Darmstadt, Germany
114 Ununquadium Uuq (285) Other metals 1998 team at the Joint Institute for Nuclear Research, Dubna, Russia
116 Ununhexium Uuh (292) Other metals 2000 team at the Joint Institute for Nuclear Research, Dubna, Russia
Chemical Reaction
Chemical Reaction, process by which atoms or groups of atoms are redistributed, resulting in a change in the molecular composition of substances. An example of a chemical reaction is formation of rust (iron oxide), which is produced when oxygen in the air reacts with iron.
The products obtained from a given set of reactants, or starting materials, depend on the conditions under which a chemical reaction occurs. Careful study, however, shows that although products may vary with changing conditions, some quantities remain constant during any chemical reaction. These constant quantities, called the conserved quantities, include the number of each kind of atom present, the electrical charge, and the total mass.
The products obtained from a given set of reactants, or starting materials, depend on the conditions under which a chemical reaction occurs. Careful study, however, shows that although products may vary with changing conditions, some quantities remain constant during any chemical reaction. These constant quantities, called the conserved quantities, include the number of each kind of atom present, the electrical charge, and the total mass.
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