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Ac
A symbol for actinium.

AcEm
(obsolete term)
A symbol for actinium emanation.

actinides
(1) Elements with atomic numbers 90 through 103 (Z=90-103), the elements that follow actinium in the periodic chart.  The set of actinides includes the following elements: 90 thorium (Th); 91 protactinium (Pa); 92 uranium (U); 93 neptunium (Np); 94 plutonium (Pu); 95 americium (Am); 96 curium (Cm); 97 berkelium (Bk); 98 californium (Cf); 99 einsteinium (Es); 100 fermium (Fm); 101 mendelevium (Md); 102 nobelium (No); 103 lawrencium (Lr).

(2) (obsolete)  The set of elements now known as actinides that are in an oxidation state of 3+.

Synonym: actinide series.
Related terms: americiumberkeliumcaliforniumcuriumeinsteiniumfermiumlawrenciummendeleviumneptuniumnobeliumperiodic tableplutoniumprotactiniumthoriumuranium.


actinide series
Synonym for actinides.

actinium
A chemical element with atomic number 89.  Actinium was discovered in 1899 by André-Louis Debierne who analyzed the pitchblende residues from the pioneering experiments of Marie and Pierre Curie.  Friedrich Giesel found actinium in 1902 although he was unaware of the work by Debierne (Giesel proposed the name emanium for this element).  The name actinium is derived from aktis, the Greek word for beam.

Symbol: Ac.
Synonym: emanium.


actinium emanation
(obsolete term)
The nuclide 219Rn.

Symbol: AcEm.

Ag
A symbol for silver.

Al
A symbol for aluminum.

alkali metals
The set of chemical elements that form group IA in the periodic chart.  The elements making up the alkali metals include lithium (Li, Z=3), sodium (Na, Z=11), potassium (K, Z=19), rubidium (Rb, Z=37), cesium (Cs, Z=55), and francium (Fr, Z=87).

Related terms: cesiumfranciumlithiumperiodic tablepotassiumrubidiumsodium.

alkaline earth metals
The set of chemical elements that form group IIA in the periodic chart.  The elements making up the alkaline earth metals beryllium (Be, Z=2), magnesium (Mg, Z=12), calcium (Ca, Z=20), strontium (Sr, Z=38), barium (Ba, Z=56), and radium (Ra, Z=88).

Related terms: bariumberylliumcalciummagnesiumperiodic tableradiumstrontium.

aluminum
A chemical element with atomic number 13.  Aluminum was first prepared in impure form in 1825 by Hans Christian Oersted.  The name aluminum is derived from alumen, the Latin word alum, which is a common aluminum-containing mineral that has been used since ancient times.

Symbol: Al

Am
A symbol for americium.

americium
A chemical element with atomic number 95.  Americium was discovered in 1944 by Glenn Seaborg, Albert Ghiorso and colleagues at the Wartime Metallurgical Laboratory, University of Chicago.  The name americium was derived from the word America.

Symbol: Am.

antimony
A chemical element with atomic number 51.  Antimony has been recognized in compounds from antiquity, and as a metal since the 17th century.  The name antimony is derived from anti and monos, Greek for metal not found alone.

Symbol: Sb.
Synonym: stibium.
Related to metalloids.


Ar
A symbol for argon.

argentum
A synonym for silver.

argon
A chemical element with atomic number 18.  Argon was discovered in 1894 by Lord Rayleigh and Sir William Ramsay.  The name argon is derived from argos, Greek for no reaction.

Symbol: Ar.
Symbol: (obsolete) A.
Related to noble gases.


arsenic
A chemical element with atomic number 33.  Arsenic has an unknown date of discovery.  Magnus obtained it in 1250, and in 1649 Schroeder published two methods for preparing aresenic.  The name arsenic is derived from arsenikos, Greek for male.

Symbol: As.
Related to metalloids.


As
A symbol for arsenic.

astatine
A chemical element with atomic number 85.  Astatine was discovered in 1940 by Emilio Segré and colleagues at the University of California, Berkeley.  Astatine was produced by irradiating 200Bi with alpha particles.  The name astatine is derived from astatos, Greek for unstable.

Symbol: At.
Related to halogens.


At
A symbol for astatine.

Au
A symbol for gold.

ausonium
(obsolete term)
A synonym for lanthanum.

Ba
A symbol for barium.

barium
A chemical element with atomic number 56.  Barium was discovered in 1808 by Sir Humphry Davy.  The name barium is derived from barys, Greek for heavy.

Symbol: Ba.
Synonym: hesperium.
Related to alkaline earth metals.


Be
A symbol for beryllium.

berkelium
A chemical element with atomic number 97.  Berkelium was discovered in 1949, by Glenn Seaborg and colleagues, when 241Am was irradiated with alpha particles to produce 243Bk.  The name berkelium is derived from University of California at Berkeley, its place of discovery.

Symbol: Bk.
Related to actinides.


beryllium
A chemical element with atomic number 4.  Beryllium was discovered as the oxide in 1798 by Louis-Nicolas Vauquelin, and was first isolated by Wöhler in 1828.  The name beryllium is derived from the Greek word beryl.

Symbol: Be.
Synonym: glucinium.
Related to alkaline earth metals.


Bi
A symbol for bismuth.

bismuth
A chemical element with atomic number 83.  Bismuth was discovered in 1753 by Claude Geoffrey when he distinguished it from lead and tin.  The name bismuth is derived from weisse masse, German for white mass.

Symbol: Bi.

Bk
Symbol for berkelium.

bohrium
A chemical element with atomic number 107.  Bohrium was discovered in 1976 by a team of scientists at the Joint Institute for Nuclear Research at Dubna in Russia.  The name neilsborium was given in honor of Niels Bohr.

Symbol: Bh.
Synonym: (obsolete) neilsbohrium.
Synonym: (obsolete) unnilseptium.
Related to transition metals.


boron
A chemical element with atomic number 5.  Boron was discovered in 1808 by Sir Humphry Davy and independently by Joseph Louis Gay-Lussac, and Louis-Jacques Thenard.  It was discovered when boron oxide was heated with potassium metal, producing the residue boron.  The name boron is derived from the Persian word burah.

Symbol: B.
Related to metalloids.


Br
A symbol for bromine.

brevium
(obsolete term)
A synonym for protactinium.

bromine
A chemical element with atomic number 35.  Bromine was discovered in 1826 by Antonie-Jérôme Balard who extracted chlorine from natural brines from the Mediterranean Sea.  The name bromine is derived from bromos, Greek for bad smell.

Symbol: Br.
Related to halogens.


C
A symbol for carbon.

Ca
A symbol for calcium.

cadmium
A chemical element with atomic number 48.  Cadmium was discovered in 1817 by Friedrich Strohmeyer while he was conducting experiments on zinc carbonate.  Later that year two other scientists independently found cadmium in samples of zinc oxide.  The name cadmium is derived from kadmeia, Greek for calamine.

Symbol: Cd.
Related to transition metals.


calcium
A chemical element with atomic number 20.  Calcium was discovered independently in 1808 by Sir Humphry Davy and by Berzelius and Pontin.  The name calcium is derived from calyx, Latin for lime (which is primarily calcium carbonate).

Symbol: Ca.
Related to alkaline earth metals.


californium
A chemical element with atomic number 98.  Californium was discovered in 1950 by Glenn Seaborg, Albert Ghiorso, Stanley Thompson, and colleagues at the University of California, Berkeley.  It was produced when scientists irradiated a microgram of 242Cm with helium ions.  The name californium is derived from University of California at Berkeley.

Symbol: Cf.
Related to actinides.


carbon
A chemical element with atomic number 6.  Carbon has been known since prehistoric times.  The name carbon is derived from carbo, Latin for charcoal.

Symbol: C.

carbon-14
A naturally-occurring radioactive isotope of carbon that has a half-life of 5730 years.  High-energy neutrons, produced in the upper atmosphere by cosmic ray interaction, react with 14N through the (n,p) reaction to form 14C.  This radioactive carbon eventually mixes with carbon in the lower atmosphere, thereby making 14C naturally available.  Ancient sources of carbon, such as coal or petroleum deposits, are too old to contain 14C: the radioactive carbon has decayed away.

Symbol: 14C.

cassiopeium
(obsolete term)
A synonym for lutetium.

Symbol: Cp.

Cd
A symbol for cadmium.

Ce
A symbol for cerium.

cerium
A chemical element with atomic number 58.  Cerium was discovered in 1803 by Martin Heinrich Klaproth and by Berzelius and Hissinger.  The name cerium is derived from the asteroid Ceres.

Symbol: Ce.
Related terms: cerium earthslanthanidesrare earths.


cerium earths
Elements with atomic numbers 57 through 62.  The set of cerium earths includes the following elements: 57 lanthanum (La); 58 cerium (Ce); 59 praseodymium (Pr); 60 neodymium (Nd); 61 promethium (Pm); 62 samarium (Sm).

Related terms: ceriumlanthanumneodymiumperiodic tablepraseodymiumpromethiumsamarium.

cesium
A chemical element with atomic number 55.  Cesium was discovered by spectroscopic analysis in 1860 by Robert Bunsen and Gustav Kirchoff.  The name cesium is derived from caesius, Latin for sky blue.

Symbol: Cs.
Synonym: caesium.
Related to alkali metals.


Cf
Symbol for californium.

chlorine
A chemical element with atomic number 17.  Chlorine was first noticed in 1774 by Carl Wilhelm Scheele who thought it was a part of oxygen.  In 1810, Humphry Davy proved that it was an independent element and named the element chlorine.  The name chlorine is derived from chloros, Greek for greenish-yellow.

Symbol: Cl.
Related to halogens.


chromium
A chemical element with atomic number 24.  Chromium was discovered in 1797 by Louis-Nicolas Vauquelin.  The name chromium is derived from chroma, Greek for colorful.

Symbol: Cr.
Related to transition metals.


Cl
A symbol for chlorine.

Cm
A symbol for curium.

cobalt
A chemical element with atomic number 27.  Cobalt was discovered by Brandt in 1735.  The name cobalt is derived from Kobold, an evil German spirit, and results from the interference of Cobalt in Copper mining.  Until 1540, it was believed that the cobalt mineral was unusable.  Adding the mineral to glass produces a bright blue color (from which we get the phrase cobalt blue).

Symbol: Co.
Related to transition metals.


columbium
A synonym for niobium.

copper
A chemical element with atomic number 29.  Copper is known from antiquity and has been mined for over 5,000 years.  The name copper is derived from Kobber, an island in Cyprus.

Symbol: Cu.
Synonym: cuprum.
Related to transition metals.


Cp
(obsolete term)
A symbol for cassiopeium which is an obsolete synonym for lutetium.


Cr
A symbol for chromium.

Cs
A symbol for cesium.

cuprum
A synonym for copper.

curium
A chemical element with atomic number 96.  Curium was discovered in 1944 by James, Ghiorso, and Seaborg.  It was created by the irradiating of 239Pu with helium ions in the 60-inch cyclotron at the University of California, Berkeley.  The name curium was given in honor of Pierre and Marie Curie.

Symbol: Cm.
Related to actinides.


D
A symbol for deuterium.

deuterium
An isotope of hydrogen which has a single proton and a single neutron.  Deuterium is a stable, naturally occurring nuclide found with an isotopic abundance of 1 part in every 7,000 parts of 1H.  A deuterium nucleus is often referred to as a deuteron.  The name was proposed by Bohr and Heisenberg.

Symbol: 2H.
Symbol: D.
Synonym: diplogen.
Synonym: heavy hydrogen.
Related terms: deuteronhydrogentritium.


dubnium
A chemical element with atomic number 105.

Symbol: Db.
Synonym: (obsolete) hahnium.
Synonym: (obsolete) unnilpentium.
Related to transition metals.


Dy
A symbol for dysprosium.

dysprosium
A chemical element with atomic number 66.  Dysprosium was discovered in 1866 by Paul-émile Lecoq de Boisbaudran.  In 1950, Spedding and associates were able to isolate the element through the separation techniques of ion-exchange and metallographic reduction.  The name dysprosium is derived from dysprositos, Greek for hard to get.

Symbol: Dy.
Related terms: lanthanidesrare earthsterbium earths.


einsteinium
A chemical element with atomic number 99.  Einsteinium Albert Ghiorso, Glenn Seaborg, and colleagues discovered Einsteinium by studying debris from a 1952 thermonuclear explosion that occurred in the South Pacific.  The name einsteinium was given in honor of Albert Einstein.

Symbol: Es.

element
(1) One or more nuclides, or a population of such nuclides with a specific number of protons.  A chemical element.

(2) The chemical elements uranium or plutonium.

element X
(obsolete term)
A synonym for holmium.

Em
A symbol for emanation.

emanation
(obsolete term)
Symbol: Em.
A synonym for radon.


emanon
(obsolete term)
A synonym for radon.

Er
A symbol for erbium.

erbium
A chemical element with atomic number 68.  Erbium was discovered in 1843 by Carl Gustaf Mosander.  The name erbium is derived from Ytterby, a town in Sweden, the place of discovery.

Symbol: Er.
Related terms: lanthanidesrare earthsyttrium earths.


Es
A symbol for einsteinium.

Eu
A symbol for europium.

europium
A chemical element with atomic number 63.  Europium was discovered in 1890 by Paul-émile Lecoq de Boisbaudran who was conducting experiments on compounds of samarium and gadolinium.  In his experiments, de Boisbaudran noticed spectral lines which he suggested were due to a new element that he was never able to isolate.  In 1901 Eugène-Anatole Demarçay was credited for the discovery of europium because he was able to successfully isolate it.  The name europium is derived from Europe.

Symbol: Eu.
Related terms: lanthanides.;  rare earths.;  terbium earths.


F
A symbol for fluorine.

Fe
A symbol for iron.

fermium
A chemical element with atomic number 100.  Fermium was reported to have been discovered in 1952 when Albert Ghiorso, Glenn Seaborg, and associates at the University of California Radiation Laboratory, Argonne National Laboratory, and Los Alamos National Laboratory were testing debris of a thermonuclear explosion in the South Pacific during the same year.  Fermium was actually discovered some time during World War II but its announcement was delayed because of security concerns.  The name fermium was given in honor of Enrico Fermi.

Symbol: Fm.
Related to actinides.


fluorine
A chemical element with atomic number 9.  Fluorine was discovered by Scheele in 1771, and was isolated by Henri Moissan in 1866 when he electrolyzed potassium hydrogen fluoride with hydrochloric acid.  The name fluorine is derived from fluere, French for flow.

Symbol: F.
Related to halogens.


Fm
A symbol for fermium.

Fr
A symbol for francium.

francium
A chemical element with atomic number 87.  Francium was discovered in 1939 by Marguerite Perey, a student at the Curie Institute in Paris, who was conducting experiments on actinium.  The name francium was given in honor of France.  The only isotope of francium that occurs in nature is 223Fr, a member of the actinium decay chain.

Symbol: Fr.
Related to alkali metals.


Ga
A symbol for gallium.

gadolinium
A chemical element with atomic number 64.  Gadolinium was discovered independently by two scientists.  In 1880, Jean-Charles Marignac isolated the metallic oxide of gadolinium from the mineral samarskite.  In 1886, Paul-émile Lecoq de Boisbaudran was able to isolate the element in fairly pure form.  The two scientists agreed to name the element gadolinium in recognition of the Finnish chemist, Johan Gadolin.

Symbol: Gd.
Related terms: cerium earthslanthanidesrare earths.


gallium
A chemical element with atomic number 31.  Gallium was discovered by spectral analysis in 1875 by Paul émile Lecoq de Boisbaudran.  The name gallium is derived from Gallia, Latin for Gaul, ancient France.

Symbol: Ga.

Gd
A symbol for gadolinium.

Ge
A symbol for germanium.

germanium
A chemical element with atomic number 32.  Germanium was discovered in 1886 by Clemens Alexander Winkler.  The name germanium was given in honor of Germany.

Symbol: Ge.
Related to metalloids.


gold
A chemical element with atomic number 79.  Gold has been known from antiquity.

Symbol: Au.
Synonym: aurum.
Related to transition metals.


H
A symbol for hydrogen.

Ha
A symbol for hahnium.

hafnium
A chemical element with atomic number 72.  Hafnium was discovered in 1932 by Dirk Coster and Georg de Hevesy who identified x-rays consistent with element 72 during x-ray spectroscopy studies on the mineral zircon.  The name hafnium is derived from Hafnia, the Latin name for Copenhagen.

Symbol: Hf.
Related to transition metals.


hahnium
(obsolete term)
A synonym for dubnium.

Symbol: Ha.

halides
Of or pertaining to two or more halogens that have an oxidation state of -1.

Related terms: astatinebrominechlorinefluorinehalogensiodine.

halogens
The set of chemical elements that form group VIIA in the periodic chart.  Halogen is derived from the Greek term for salt former as the elements will react with metals to form salts.  The elements making up the halogens include fluorine (F, Z=9), chlorine (Cl, Z=17), bromine (Br, Z=35), iodine (I, Z=53), and astatine (At, Z=85).

Related terms: astatinebrominechlorinefluorinehalideiodineastatine.

hassium
A chemical element with atomic number 108.

Symbol: Hs.
Synonym: (obsolete) unniloctium.
Related to transition metals.


He
A symbol for helium.

heavy hydrogen
A synonym for deuterium.

helium
A chemical element with atomic number 2.  Helium was first observed in 1868 by Pierre-Jules-César Janssen who identified a new spectral line in a solar spectrum during a solar eclipse.  Later that year Jospeh Norman Lockyer concluded that Janssen had discovered a new element, one that had yet to be found on earth.  The name helium is derived from helios, Latin for sun.

Symbol: He.
Related to noble gases.


Hf
A symbol for hafnium.

Hg
A symbol for mercury.

Ho
A symbol for holmium.

holmium
A chemical element with atomic number 67.  Holmium was first observed in 1878 by Jacques Soret and Marc Delafonatine who named it Element X.  Swedish chemist, Per Teodor Cleve was credited for the discovery when he obtained a sample of holmium from the mineral erbia.  The name holmium is derived from Holmia, Latin for Stockholm.

Symbol: Ho.
Synonym: (obsolete) element X.
Related terms: lanthanidesrare earthsyttrium earths.


Hs
A symbol for hassium.

hydrogen
A chemical element with atomic number 1.  Hydrogen was discovered in 1766 by Henry Cavendish.  In his experiments, Cavendish demonstrated that hydrogen would explode in air and so the element was referred to as fire air.  Further experiments proved that hydrogen, when combined with oxygen, made up water.  The name hydrogen is derived from hydros-gen, Greek for water producing.

Symbol: H.
Synonym: (obsolete) hyplogen.
Synonym: (obsolete) protium.


hyplogen
(obsolete term) A name Rutherford proposed in 1932 for the nuclide 1H, hydrogen.

A synonym for hydrogen.

I
A symbol for Iodine.

In/font>
A symbol for indium.

indium
A chemical element with atomic number 49.  Indium was discovered by spectral analysis in 1863 by Ferdinand Reich and Theodor Richter.  The name indium is derived from the Latin word indigo.

Symbol: In.

iodine
A chemical element with atomic number 53.  Iodine was discovered in 1811 by Bernard Courtois who was conducting experiments on salt water brines.  The name iodine is derived from iodes, Greek for violet.

Symbol: I.
Related to halogens.


Ir
A symbol for iridium.

iridium
A chemical element with atomic number 77.  Iridium was discovered in 1803 by Smithsonian Tennant who was conducting experiments on crude platinum.  The name iridium is derived from iris, Latin for rainbow colors.

Symbol: Ir.
Related to transition metals.


iron
A chemical element with atomic number 26.  Iron has been known from antiquity.  The name iron is derived from the Latin word ferrum.

Symbol: Fe.
Related to transition metals.


K
A symbol for potassium.

Kr
A symbol for krypton.

krypton
A chemical element with atomic number 36.  Krypton was discovered in the residue of liquified air in 1898 by Sir William Ramsay and Morris William Traverse.  The name krypton is derived from kryptos, Greek for hidden.

Symbol: Kr.
Related to noble gases.


kurchatovium
(obsolete term)
A synonym for rutherfordium.

La
A symbol for lanthanum.

lanthanide group
A synonym for lanthanides.

lanthanides
Elements with atomic numbers 58 through 71 (Z=57-71), the elements that follow lanthanum in the periodic chart.  The set of lanthanides includes the following elements: cerium (Ce, Z=58); praseodymium (Pr, Z=59); neodymium (Nd, Z=60); promethium (Pm, Z=61); samarium (Sm, Z=62); europium (Eu, Z=63); gadolinium (Gd, Z=64); terbium (Tb, Z=65); dysprosium (Dy, Z=66); holmium (Ho, Z=67); erbium (Er, Z=68); thulium (Tm, Z=69); ytterbium (Yb, Z=70); lutetium (Lu, Z=71).

Synonym: lanthanide group.
Synonym: lanthanide series.
Synonym: lanthanons.
Related terms: ceriumdysprosiumerbiumeuropiumgadoliniumholmiumlanthanumlutetiumneodymiumperiodic tablepraseodymiumpromethiumrare earthssamariumterbiumthuliumytterbium.


lanthanide series
A synonym for lanthanides.

lanthanons
A synonym for lanthanides.

lanthanum
A chemical element with atomic number 57.  Lanthanum was discovered in 1839 by Carl Gustaf Mosander who separated its oxide from cerium oxide.  The name lanthanum is derived from lanthanein, Greek for that which is hidden.

Symbol: La.
Synonym: (obsolete) ausonium.
Related terms: cerium earthslanthanidesrare earths.


lawrencium
A chemical element with atomic number 103.  Lawrencium was discovered in 1965 by a team of Soviet scientists at the Joint Institute for Nuclear Research in Dubna, Russia.  The name lawrencium was given in honor of Ernest O. Lawrence, inventor of the cyclotron.

Symbol: Lr.
Related to actinides.


lead
A chemical element with atomic number 82.  Lead has been known from antiquity.  The name lead is derived from plumbum, the Latin meaning heavy.

Symbol: Pb.
Synonym: plumbum.


Li
A symbol for lithium.

lithium
A chemical element with atomic number 3.  Lithium was discovered in 1817 by Johan August Arfvedson.  The name lithium is derived from lithos, Greek for stone.

Symbol: Li.
Related to alkali metals.


Lr
A symbol for lawrencium.

Lu
A symbol for lutetium.

lutetium
A chemical element with atomic number 71.  Lutetium was discovered in 1907 independently discovered by Carl Auer von Welsbach and Georges Urbain.  The name lutetium is derived from Lutetia, Latin for Paris (France).

Symbol: Lu.
Synonym: cassiopeium.
Related terms: lanthanidesrare earthsyttrium earths.


manganese
A chemical element with atomic number 25.  Manganese was noticed by Karl Wilhelm Scheele years before its discovery by Johan Gottlieb Gahn, in 1774, who successfully isolated it by reducing carbon with dioxide.  The name manganese is derived from magnes, Latin for magnet.

Symbol: Mn.
Related to transition metals.


magnesium
A chemical element with atomic number 12.  Magnesium was recognized in 1755 by Black and was first isolated by Sir Humphry Davy in 1808.  The name magnesium was given in honor of Mangan, an area in Greece.

Symbol: Mg.
Related to alkaline earth metals.


masurium
(obsolete term)
A synonym for technetium.

Md
A symbol for mendelevium.

meitnerium
A chemical element with atomic number 109.  Meitnerium was discovered in 1982 by a team of scientists at the Heavy Ion Research Laboratory in Darmstadt, West Germany.  The name meitnerium was given in honor of Lise Meitner.

Symbol: Mt.
Related to transition metals.


mendelevium
A chemical element with atomic number 101.  Mendelevium was discovered in 1955 by Albert Ghiorso, Glenn Seaborg, and associates at the University of California, Berkeley.  The name mendelevium was given in honor of Dmitri Mendeleev

Symbol: Md.
Related to actinides.


mercury
A chemical element with atomic number 80.  Mercury has an unknown date of discovery, but it has been found in Ancient Egyptian tombs dating back to 1500 BC.  The name mercury was derived from the planet Mercury.

Symbol: Hg.
Related to transition metals.


metalloids
The set of chemical elements that form a sort of boundary in the periodic chart between the metals and non-metals.  The elements making up the metalloids include boron (B, Z=5), silicon (Si, Z=14), germanium (Ge, Z=32), arsenic (As, Z=33), antimony (Sb, Z=51), tellurium (Te, Z=52), and polonium (Po, Z=84).

Related terms: antimonyarsenicborongermaniumperiodic tablepoloniumsilicontellurium.

Mg
A symbol for magnesium.

Mn
A symbol for manganese.

Mo
A symbol for molybdenum.

molybdenum
A chemical element with atomic number 42.  Molybdenum was discovered in 1778 by Carl Wilhelm Scheele.  Previous to Scheele's discovery, scientists believed that molybdenite was a graphite ore.  The name molybdenum is derived from molybdos, Greek for lead.

Symbol: Mo.
Related to transition metals.


Mt
A symbol for meitnerium.

N
A symbol for nitrogen.

Na
A symbol for sodium.

natrium
A synonym for sodium.

Nb
A synonym for niobium.

Nd
A symbol for neodymium.

Ne
A symbol for neon.

neilsbohrium
(obsolete term)
A synonym for bohrium.

Symbol: Ns.

neodymium
A chemical element with atomic number 60.  Neodymium was discovered in 1885 by Carl Auer von Welsbach in samples of didymium.  The name neodymium is derived from neos and didymos, Greek for new and twins.

Symbol: Nd.
Related terms: cerium earthslanthanidesrare earths.


neon
A chemical element with atomic number 10.  Neon was discovered in 1898 by Alexander Ramsay and Morris William Travers in the residue of an experiment on a sample of hydrogen.  The name neon is derived from neos, Greek for new.

Symbol: Ne.
Related to noble gases.


neptunium
A chemical element with atomic number 93.  Neptunium was discovered in 1940 by Philip Hauge Abelson and Edwin McMillan who irradiated <sup>238</sup>U with neutrons.  It was the first man-made transuranic element.  Neptunium was named after the planet Neptune.

Symbol: Np.

Ni
A symbol for nickel.

nickel
A chemical element with atomic number 28.  Nickel was discovered in 1751 by Axel Fredrik Cronstedt in the mineral niccolite.  The name nickel is derived from the German for Satan.

Symbol: Ni.
Related to transition metals.


niobium
A chemical element with atomic number 41.  Niobium was discovered in 1801 by Charles Hatchett who named it columbium.  In 1950, it was renamed niobium by the International Union of Pure and Applied Chemistry.  The name niobium was named after the mythological creature Niobe, daughter of Tantalus.

Symbol: Nb.
Synonym: columbium.
Related to transition metals.


nipponium
(obsolete term)
A synonym for technetium.

niton
(obsolete term)
Symbol: Nt.
A synonym for radon.


nitrogen
A chemical element with atomic number 7.  Nitrogen was independently discovered in 1772 by Daniel Rutherford, Jospeh Priestly, Karl Wilhelm Scheele, and Henry Cavendish, but Rutherford is usually credited for its discovery.  The name nitrogen is derived from nitrum, Latin for soda producing.

Symbol: N.

No
A symbol for nobelium.

nobelium
A chemical element with atomic number 102.  Nobelium was discovered in 1957 by Albert Ghiorso, Glenn Seaborg, and associates at the University of California at Berkeley.  Nobelium was named after Alfred Nobel who discovered dynamite.

Symbol: No.
Related to actinides.


noble gases
The set of chemical elements that form group VIIIA in the periodic chart.  Noble gases have a closed shell of electrons and are thus chemically relatively inert.  The elements making up the noble gases include helium (He, Z=2), neon (Ne, Z=10), argon (Ar, Z=18), krypton (Kr, Z=36), xenon (Xe, Z=54), and radon (Rn, Z=86).

Acronym: NG.
Synonym: inert gases.
Synonym: rare gases.
Related terms: argonheliumkryptonneonperiodic chartradonxenon.


Np
A symbol for neptunium.

Ns
A symbol for nielsbohrium.

Nt
A symbol for niton.

O
A symbol for oxygen.

Os
A symbol for osmium.

osmium
A chemical element with atomic number 76.  Osmium was discovered in 1803 by Charles Tennant while conducting experiments on crude platinum and aqua regina.  The name osmium is derived from osme, Greek for an odd smell.

Symbol: Os.
Related to transition metals.


oxygen
A chemical element with atomic number 8.  Although Karl Wilhelm Scheele first observed oxygen in 1772, Joseph Prisetly is credited with its 1775 discovery.  The name oxygen is derived from oxys, Greek for acid producing.

Symbol: O.

P
A symbol for phosphorus.

Pa
A symbol for protactinium.

palladium
A chemical element with atomic number 46.  Palladium was discovered in 1803 by William Hyde Wollaston in deposits of platinum.  The name palladium was derived from the asteroid Pallas.  Pallas is also the Greek goddess of wisdom.

Symbol: Pd.
Related to transition metals.


Pb
A symbol for lead.

Pd
A symbol for palladium.

periodic table
A table showing the chemical elements ordered by atomic number and grouped roughly according to the electron structure of the last valence electron.

Related terms: actinidesalkali metalsalkaline earth metalscerium earthschart of nuclideshalogenslanthanidesnoble gasesrare earthsterbium earthstransition metalsyttrium earths.

phosphorus
A chemical element with atomic number 15.  Phosphorus was discovered in 1669 by Hennig Brand while he was conducting experiments on urine.  The name phosphorus is derived from phosphoros, Greek for bearing light.  Phosphorus is also the ancient name for the planet Venus.

Symbol: P.

platinum
A chemical element with atomic number 78.  Platinum was used by pre-Columbian Indians, but it was not until 1735 that Ulloa discovered, isolated, and named the element.  The name platinum is derived from platina, Spanish for silver.

Symbol: Pt.
Related to transition metals.


plutonium
A chemical element with atomic number 94.  Plutonium was discovered in 1940 by Seaborg, McMillan, Wahl and Kennedy at the University of California, Berkeley.  The group irradiated uranium with deuterons in a 60-inch cyclotron.  The name plutonium was given in honor of the planet Pluto.  Seaborg often said he and his colleagues assigned the symbol Pu for plutonium as a prank as it stood for something that smelled bad.  They never believed the community would accept Pu as the adopted symbol.

Symbol: Pu.

Pm
A symbol for promethium.

Po
A symbol for polonium.

polonium
A chemical element with atomic number 84.  Polonium was discovered in 1898 by Marie Sklodowska Curie.  The name polonium was given in honor of Poland, the homeland of its discoverer, Marie Curie.

Symbol: Po.
Related to metalloids.


potassium
A chemical element with atomic number 19.  Potassium was discovered in 1807 by Sir Humphry Davy who conducted experiments on potash.  The name potassium is derived from the English words potash ore.

Symbol: K.
Synonym: kalium.
Related to alkali metals.


Pr
A symbol for praseodymium.

praeseodymium
A synonym for praseodymium.

praseodymium
A chemical element with atomic number 59.  Praseodymium first isolated in 1885 by Karl Auer von Welsbach who isolated praseodymium and neodymium from the mineral dydimia.  The name praesodymium is derived from prasios and didymos, Greek for green and twin.

Symbol: Pr.
Synonym: praeseodymium.
Related terms: cerium earthslanthanidesrare earths.


promethium
A chemical element with atomic number 61.  Promethium was discovered in 1945.  The name promethium was is derived from the mythological creature Prometheus who stole fire from the heavens, giving it to humans.

Symbol: Pm.
Related terms: cerium earthslanthanidesrare earths.


protactinium
A chemical element with atomic number 91.  Protactinium was discovered in 1913 by Kasimir Fajans although he named it brevium.  In 1918, the elements name was permanently changed to protactinium when Otto Hahn and Lise Meitner identified the nuclide 238Pa.  The name protactinium is derived from protos, Greek for first.

Symbol: Pa.
Synonym: (obsolete) brevium.
Synonym: (obsolete) protoactinium.
Related to actinides.


protium
(obsolete term)
An early proposed name for the nuclide 1H, hydrogen.

A synonym for hydrogen.

protoactinium
(obsolete term)
A synonym for protactinium.

Pt
A symbol for platinum.

Pu
A symbol for plutonium.

Ra
A symbol for radium.

radium
A chemical element with atomic number 88.  Radium was discovered in 1898 by Marie Sklodowska Curie in an ore of pitchblende.  In 1911 Curie and André Debierne successfully isolated radium by electrolysis.  The name radium is derived from radius, Latin for ray.

Symbol: Ra.
Related to alkaline earth metals.


radium emanation
(obsolete term)

The nuclide 222Rn.

Symbol: RaEm.

radon
A chemical element with atomic number 86.  Radon was discovered in 1900 by Friedrich Ernst Dorn.  The name radon is derived from radius, Latin for ray.

Symbol: Rn.
Synonym: (obsolete) emanation.
Synonym: (obsolete) emanon.
Synonym: (obsolete) niton.


RaEm
A symbol for radium emanation.

rare earths
The lanthanides including sometimes scandium and yttrium.

Related terms: ceriumdysprosiumerbiumeuropiumgadoliniumholmiumlanthanideslanthanumlutetiumneodymiumperiodic tablepraseodymiumpromethiumsamariumscandiumterbiumthuliumytterbiumyttrium.

rare gases
A synonym for noble gases.

Rb
A symbol for rubidium.

Re
A symbol for rhenium.

Rf
A synonym for rutherfordium.

Rh
A symbol for rhodium.

rhenium
A chemical element with atomic number 75.  Rhenium was discovered in 1925 by Otto Berg, Karl Friedrich Noddack, and Ida Tacke during experiments on platinum ore and the mineral columbite.  The name rhenium is derived from the Latin word rhenus.

Symbol: Re.
Related to transition metals.


rhodium
A chemical element with atomic number 45.  Rhodium was discovered in 1803 by William Hyde Wollaston during experiments on crude platinum ore.  The name rhodium is derived from rhodon, Greek for rose colored.

Symbol: Rh.
Related to transition metals.


Rn
A symbol for radon.

Ru
A symbol for ruthenium.

rubidium
A chemical element with atomic number 37.  Rubidium was discovered in 1860 by Robert Bunsen and Gustav Kirchoff in the mineral lepidolite.  The name rubidium is derived from rubidus, Latin for deep red colored.

Symbol: Rb.
Related to alkali metals.


ruthenium
A chemical element with atomic number 44.  Ruthenium was discovered in 1844 by Karl Klaus in a sample of crude platinum.  The name ruthenium is derived from Ruthenia, Latin for Russia.

Symbol: Ru.
Related to transition metals.


rutherfordium
A chemical element with atomic number 104.  Rutherfordium was discovered in 1964 by a team of scientists at the Joint Institute for Nuclear Research at Dubna in Russia who named the element kurchatovium.  The Russian scientists were unable to duplicate their results and therefore lost credit to a team of scientists at the University of California, Berkeley, who identified the element.  The scientists in California were successful in isolating the element after irradiating 249Cf with 12C.  The name rutherfordium was given in honor of Ernest Rutherford.

Symbol: Rf.
Synonym: (obsolete) kurchatovium.
Synonym: (obsolete) unnilquadium.
Related to transition metals.


S
A symbol for sulfur.

samarium
A chemical element with atomic number 62.  Samarium was discovered in 1879 by Paul-émile Lecoq de Boisbaudran in an impure oxide of the mineral samarskite.  The name samarium comes from the mineral samarskite.

Symbol: Sm.
Related terms: cerium earthslanthanidesrare earths.


name = "Sb">Sb
A symbol for antimony.

Sc
A symbol for scandium.

scandium
A chemical element with atomic number 21.  Scandium was discovered in 1879 by Lars Fredrik Nilson in experiments on the minerals euxenite and gadolinite.  The name scandium is derived from Scandia, the Latin name for Scandinavia.

Symbol: Sc.
Related terms: rare earthstransition metals.


Se
A symbol for selenium.

seaborgium
A chemical element with atomic number 106.  Seaborgium was first observed in June, 1974 by a team of scientists at the Joint Institute for Nuclear Research at Dubna in Russia.  In September of that year, scientists at the Lawrence Berkeley Laboratory and the Lawrence Livermore Laboratory confirmed the discovery of element 106.  The Russian and American scientists could not agree on a name, so it remained unnamed until 1997 when the International Union for Pure and Applied Chemistry and the American Chemical Society officially named it seaborgium after the chemist Glenn Seaborg.

Symbol: Sg.
Synonym: (obsolete) unnilhexium.
Related to transition metals.


selenium
A chemical element with atomic number 34.  Selenium was discovered in 1817 by Jöns Jakob Berzelius who was conducting experiments on the element tellurium.  The name selenium is derived from selene, Greek for moon.

Symbol: Se.

Sg
A symbol for seaborgium.

Si
A symbol for silicon.

silicon
A chemical element with atomic number 14.  Silicon was discovered in 1824 by Jöns Jakob Berzelius.  The name silicon is derived from silicis, Latin for flint.

Symbol: Si.
Related to metalloids.


silver
A chemical element with atomic number 47.  Silver has been known from antiquity.  Dumps in Asia Minor show that humans began mining silver as far back as 3,000 BC.  The name silver is derived from aregentum, Latin for shining.

Symbol: Ag.
Synonym: argentum.
Related to transition metals.


Sm
A symbol for samarium.

sodium
A chemical element with atomic number 11.  Sodium has an unknown date of discovery.  A sodium carbonate, called natron, dated back to early times in Egypt where it has been found in vases and tombs.  In 1807 Humphry Davy first isolated sodium in 1807 in experiments on the electrolysis of soda.  The name sodium is derived from the English word soda.

Symbol: Na.
Synonym: natrium.
Related to alkali metals.


Sr
A symbol for strontium.

stibium
A synonym for antimony.

strontium
A chemical element with atomic number 38.  Strontium was discovered in 1808 by Humphry Davy who successfully isolated it after electroyzing lime and mercury.  The name strontium is derived from Strontian, a town in Scotland.

Symbol: Sr.
Related to alkaline earth metals.


sulfur
A chemical element with atomic number 16.  Sulfur has been known from antiquity.  The name sulfur is derived from the Latin word sulphur.

Symbol: S.

T
A symbol for tritium.

Ta
A symbol for tantalum.

tantalum
A chemical element with atomic number 73.  Tantalum was discovered in 1802 by Anders Gustav Ekeberg.  The name tantalum is derived from the mythological creature Tantalos, father of Niobe.

Symbol: Ta.
Related to transition metals.


Tb
A symbol for terbium.

Tc
A symbol for technetium.

Te
A symbol for tellurium.

technetium
A chemical element with atomic number 43.  Technetium was discovered in 1937 at the University of California at Berkeley by Enrico Fermi and Carlo Perrier.  The longest lived isotope of technetium is 98Tc which has a half life of 1.5 billion years.

Symbol: Tc.
Synonym: (obsolete) masurium.
Synonym: (obsolete) nipponium.
Related to transition metals.


tellurium
A chemical element with atomic number 52.  Tellurium was discovered by Joseph Müller von Reichenstein in 1782 but was not named until Martin Heinrich Klaproth isolated it in 1798.  The name tellurium is derived from tellus, Latin for earth.

Symbol: Te.
Related to metalloids.


terbium
A chemical element with atomic number 65.  Terbium was discovered in 1843 by Carl Gustaf Mosander while he was conducting experiments on the minerals gadolinite and yttria.  The name terbium is derived from Ytterby, a town in Sweden, the place of discovery.

Symbol: Tb.
Related terms: lanthanidesrare earthsterbium earths.


terbium earths
Elements with atomic numbers 63 through 66.  The set of cerium earths includes the following elements: 63 europium (Eu); 64 gadolinium (Gd); 65 terbium (Tb); 66 dysprosium (Dy).

Related terms: dysprosiumeuropiumgadoliniumperiodic tableterbium.

Th
A symbol for thorium.

thallium
< A chemical element with atomic number 81.  Thallium was discovered in 1861 by Sir William Crookes who successfully isolated it the following year.

Symbol: Tl.

ThEm
A symbol for thoron emanation.

thorium
A chemical element with atomic number 90.  Thorium was discovered in 1828 by Jöns Jakob Berzelius in the mineral monazite.  The name thorium is derived from Thor, the Scandinavian god of war.

Symbol: Th.
Related to actinides.


thoron emanation
(obsolete)
The nuclide 220Rn.

Symbol: ThEm.

thulium
A chemical element with atomic number 69.  Thulium was discovered in 1879 by Per Teodor Cleve.  The name thulium was given in honor of Thule, the ancient name of Scandinavia.

Symbol: Tm.
Symbol: (obsolete) Tu.
Related terms: lanthanidesrare earthsyttrium earths.


Ti
A symbol for titanium.

tin
A chemical element with atomic number 50.  Tin has been known from antiquity.  The name tin is derived from stannum, Latin for dripping and easily melted.

Symbol: Sn.
Synonym: stannum.


titanium
A chemical element with atomic number 22.  Titanium was discovered in 1791 by William Gregor.  The name titanium was given in honor of Titans, the first sons of the earth.

Symbol: Ti.
Related to transition metals.


Tl
A symbol for thallium.

Tm
A symbol for thulium.

transition metals
The set of chemical elements in groups IB through VIIB and group VIII in the periodic table.  The transition metals includes the elements scandium (Sc, Z=21), titanium (Ti, Z=22), vanadium (V, Z=23), chromium (Cr, Z=24), manganese (Mn, Z=25), iron (Fe, Z=26), cobalt (Co, Z=27), nickel (Ni, Z=28), copper (Cu, Z=29), zinc (Zn, Z=30), yttrium (Y, Z=39), zirconium (Zr, Z=40), niobium (Nb, Z=41), molybdenum (Mo, Z=42), technetium (Tc, Z=43), ruthenium (Ru, Z=44), rhodium (Rh, Z=45), palladium (Pd, Z=46), silver (Ag, Z=47), cadmium (Cd, Z=48), hafnium (Hf, Z=72), tantalum (Ta, Z=73), tungsten (W, Z=74), rhenium (Re, Z=75), osmium (Os, Z=76), iridium (Ir, Z=77), platinum (Pt, Z=78), gold (Au, Z=79), mercury (Hg, Z=80), rutherfordium (Rf, Z=104), dubnium (Db, Z=105), seaborgium (Sg, Z=106), bohrium (Bh, Z=107), hassium (Hs, Z=108), meitnerium (Mt, Z=109), ununnilium (Uun, Z=110), unununium (Uuu, Z=111), and ununbium (Uub, Z=112).

Related terms: bohriumcadmiumchromiumcobaltcopperdubniumgoldhafniumhassiumiridiumironmanganesemeitneriummercurymolybdenumnickelniobiumpalladiumosmiumperiodic tableplatinumrheniumrhodiumrutheniumrutherfordiumscandiumseaborgiumsilvertantalumtechnetiumtitaniumtungstenvanadiumyttriumzinczirconium

transuranic element
An element above uranium in the periodic table, one with an atomic number greater than 92.

Synonym: transuranium element.
Related to transuranium radionuclide.


transuranium element
A synonym for transuranic element.

transuranium radionuclide
Any radionuclide having an atomic number greater than 92.

Related to transuranic element.

tritium
An isotope of hydrogen with a single proton and two neutrons.  Tritium is radioactive with a half-life of 12.33 years.  It is found in nature as a result of the interaction of cosmic rays in the upper atmosphere.  A tritium nucleus is called a triton.

Symbol: 3H.
Symbol: T.
Related terms: deuteriumhydrogentriton.


Tu
(obsolete term)
A symbol for thulium.

tungsten
A chemical element with atomic number 74.  Tungsten was discovered in 1783 by Don Fasto d'Elhuyar and Juan José d'Eluhyar.  The name tungsten is derived from tung sten, Swedish for heavy stone.

Symbol: W.
Synonym: wolfram.
Related to transition metals.


U
A symbol for uranium.

unnilhexium
(obsolete term)
A synonym for seaborgium.

unniloctium
(obsolete term)
A synonym for hassium.

unnilpentium
(obsolete term)
A synonym for dubnium.

Symbol: Unp.

unnilquadium
(obsolete term)
A synonym for rutherfordium.

Symbol: Unq.

unnilseptium
(obsolete term)
A synonym for bohrium.

uranium
A chemical element with atomic number 92.  Uranium was discovered in 1789 by Martin Heinrich Klaproth though it was not until 1842 that it was successfully isolated by Eugéne-Melchior Péligot.  The name uranium is derived from the planet Uranus.

Symbol: U.

V
A symbol for vanadium.

vanadium
A chemical element with atomic number 23.  Vandium was discovered in 1801 by Andrès del Rio although he was unable to convince other scientists that it was more than just impure chromium.  Vanadium was re-discovered in 1831 by Nils Sefström, and was named after Vanadis, a Scandanavian goddess.

Symbol: V.
Related to transition metals.


W
A symbol for tungsten.

wolfram
A synonym for tungsten.

Xe
A symbol for xenon.

xenon
A chemical element with atomic number 54.  Xenon was discovered in 1898 by Alexander Ramsay and Morris William Travers while they were conducting experiments on hydrogen.  The name xenon is derived from xenon, Greek for stranger.

Symbol: Xe.
Related to noble gases.


Y
A symbol for yttrium.

Yb
A symbol for ytterbium.

ytterbium
A chemical element with atomic number 70.  Ytterbium was discovered in 1878 by Marignac.  The name ytterbium is derived from Ytterby, a town in Sweden, its place of discovery.

Symbol: Yb.
Related terms: lanthanidesrare earthsyttrium earths.


yttrium earths
Elements with atomic numbers 63 through 67.  The set of cerium earths includes the following elements: 67 holmium (Ho); 68 erbium (Er); 69 thulium (Tm); 70 ytterbium (Yb); 71 lutetium (Lu).

Related terms: erbiumholmiumlutetiumperiodic tablethuliumytterbium.

yttrium
A chemical element with atomic number 39.  Yttrium was discovered in 1794.  The name yttrium is derived from Ytterby, a town in Sweden, its place of discovery.

Symbol: Y.
Related terms: rare earthstransition metals.


zinc
A chemical element with atomic number 30.  Zinc was first recognized as a separate element by Marggrat in 1746.  The name zinc is derived from zink, German for odd origin.

Symbol: Zn.
Related to transition metals.


zirconium
A chemical element with atomic number 40.  Zirconium was first identified by Martin Henrich Klaproth in 1789.  But the discovery is credited to Jöns Jakob Berzelius who successfully isolated the element by heating potassium zirconium flouride in 1824.  The name zirconium is derived from zargun, Persian for like gold.

Symbol: Zr.
Related to transition metals.


Zn
A symbol for zinc.

Zr
A symbol for zirconium.
 
 
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