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<full_name>Elements database 20001107</full_name>
<description>00-database-info
This file was converted from the original database on:
          Mon Jan 29 05:15:08 2001


The original data is available from:
     http://ucsub.colorado.edu/~kominek/elements/

The original data was distributed with the notice shown below.  No
additional restrictions are claimed.  Please redistribute this
changed version under the same conditions and restriction that
apply to the original version.

   Elements database 20001107
   This dictionary database was created by Jay F. Kominek
   &lt;jay.kominek@colorado.edu&gt; (Feel free to send any comments, additions,
   corrections, money to that address) It was compiled from a variety of
   sources, and is in my opinion, a work of my own. (The only stuff that
   was really copied verbatim was the atomic numbers and weights, please,
   I'd like to see someone try and exert a copyright on the values of atoms.)
   So, I place this in the public domain, if it somehow breaks, you get to
   keep both pieces. It'd be nice if you kept the fact that I compiled the
   information in here, but is not needed.
   Up to date copies can probably be found on the web at:
   http://ucsub.colorado.edu/~kominek/elements/
Source url: http://ucsub.colorado.edu/~kominek/elements/</description>
<ar><k>actinium</k>
actinium
Symbol: Ac
Atomic number: 89
Atomic weight: (227)
Silvery radioactive metallic element, belongs to group 3 of the periodic
table. The most stable isotope, Ac-227, has a half-life of 217 years.
Ac-228 (half-life of 6.13 hours) also occurs in nature. There are 22 other
artificial isotopes, all radioactive and having very short half-lives.
Chemistry similar to lanthanum. Used as a source of alpha particles.
Discovered by A. Debierne in 1899.</ar>
<ar><k>aluminum</k>
aluminum
Symbol: Al
Atomic number: 13
Atomic weight: 26.9815
Silvery-white lustrous metallic element of group 3 of the periodic table.
Highly reactive but protected by a thin transparent layer of the oxide
which quickly forms in air. There are many alloys of aluminum, as well as
a good number of industrial uses. Makes up 8.1% of the Earth's crust, by
weight. Isolated in 1825 by H.C. Oersted.</ar>
<ar><k>americium</k>
americium
Symbol: Am
Atomic number: 95
Atomic weight: (243)
Radioactive metallic transuranic element, belongs to the actinoids. Ten
known isotopes. Am-243 is the most stable isotope, with a half-life of
7.95*10^3 years. Discovered by Glenn T. Seaborg and associates in 1945, it
was obtained by bombarding {uranium}-238 with alpha particles.</ar>
<ar><k>antimony</k>
antimony
Symbol: Sb
Atomic number: 51
Atomic weight: 121.75
Element of group 15. Multiple allotropic forms. The stable form of
antimony is a blue-white metal. Yellow and black antimony are unstable
non-metals. Used in flame-proofing, paints, ceramics, enamels, and rubber.
Attacked by oxidizing acids and halogens. First reported by Tholden in
1450.</ar>
<ar><k>argon</k>
argon
Symbol: Ar
Atomic number: 18
Atomic weight: 39.948
Monatomic noble gas. Makes up 0.93% of the air. Colourless, odorless. Is
inert and has no true compounds. Lord Rayleigh and Sir william Ramsey
identified argon in 1894.</ar>
<ar><k>arsenic</k>
arsenic
Symbol: As
Atomic number: 33
Atomic weight: 74.922
Metalloid element of group 15. There are three allotropes, yellow, black,
and grey. Reacts with halogens, concentrated oxidizing acids and hot
alkalis. Albertus Magnus is believed to have been the first to isolate the
element in 1250.</ar>
<ar><k>astatine</k>
astatine
Symbol: At
Atomic number: 85
Atomic weight: (210)
Radioactive halogen element. Occurs naturally from uranium and thorium
decay. At least 20 known isotopes. At-210, the most stable, has a
half-life of 8.3 hours. Synthesized by nuclear bombardment in 1940 by D.R.
Corson, K.R. MacKenzie and E. Segre at the University of California.</ar>
<ar><k>barium</k>
barium
Symbol: Ba
Atomic number: 56
Atomic weight: 137.34
Silvery-white reactive element, belonging to group 2 of the periodic
table. Soluble barium compounds are extremely poisonous. Identified in
1774 by Karl Scheele and extracted in 1808 by Humphry Davy.</ar>
<ar><k>berkelium</k>
berkelium
Symbol: Bk
Atomic number: 97
Atomic weight: (247)
Radioactive metallic transuranic element. Belongs to actinoid series.
Eight known isotopes, the most common Bk-247, has a half-life of
1.4*10^3 years. First produced by Glenn T. Seaborg and associates in 1949
by bombarding americium-241 with alpha particles.</ar>
<ar><k>beryllium</k>
beryllium
Symbol: Be
Atomic number: 4
Atomic weight: 9.0122
Grey metallic element of group 2 of the periodic table. Is toxic and can
cause severe lung diseases and dermatitis. Shows high covalent character.
It was isolated independently by F. Wohler and A.A. Bussy in 1828.</ar>
<ar><k>bismuth</k>
bismuth
Symbol: Bi
Atomic number: 83
Atomic weight: 208.980
White crystalline metal with a pink tinge, belongs to group 15. Most
diamagnetic of all metals and has the lowest thermal conductivity of all
the elements except mercury. Lead-free bismuth compounds are used in
cosmetics and medical procedures. Burns in the air and produces a blue
flame. In 1753, C.G. Junine first demonstrated that it was different from
lead.</ar>
<ar><k>bohrium</k>
bohrium
Competing name for {unnilseptium}, the 107th element, proposed by the
IUPAC in response to the discoverers of the element wanting to name it
{nielsbohrium}.</ar>
<ar><k>boron</k>
boron
Symbol: B
Atomic number: 5
Atomic weight: 10.811
An element of group 13 of the periodic table. There are two allotropes,
amorphous boron is a brown power, but metallic boron is black. The
metallic form is hard (9.3 on Mohs' scale) and a bad conductor in room
temperatures. It is never found free in nature. Boron-10 is used in
nuclear reactor control rods and shields. It was discovered in 1808 by Sir
Humphry Davy and by J.L. Gay-Lussac and L.J. Thenard.</ar>
<ar><k>bromine</k>
bromine
Symbol: Br
Atomic number: 35
Atomic weight: 79.909
Halogen element. Red volatile liquid at room temperature. Its reactivity
is somewhere between chlorine and iodine. Harmful to human tissue in a
liquid state, the vapour irritates eyes and throat. Discovered in 1826 by
Antoine Balard.</ar>
<ar><k>cadmium</k>
cadmium
Symbol: Cd
Atomic number: 48
Atomic weight: 112.40
Soft bluish metal belonging to group 12 of the periodic table. Extremely
toxic even in low concentrations. Chemically similar to zinc, but lends
itself to more complex compounds. Discovered in 1817 by F. Stromeyer.</ar>
<ar><k>caesium</k>
caesium
Symbol: Cs
Atomic number: 55
Atomic weight: 132.90545
Soft silvery-white metallic element belonging to group 1 of the periodic
table. One of the three metals which are liquid at room temperature. Cs-133
is the natural, and only stable, isotope. Fifteen other radioisotopes exist.
Caesium reacts explosively with cold water, and ice at temperatures above
157K. Caesium hydroxide is the strongest base known. Caesium is the most
electropositive, most alkaline and has the least ionization potential of
all the elements. Known uses include the basis of atomic clocks, catalyst
for the hydrogenation of some organic compounds, and in photoelectric cells.
Caesium was discovered by Gustav Kirchoff and Robert Bunsen in Germany in
1860 spectroscopically. Its identification was based upon the bright blue
lines in its spectrum. The name comes from the latin word caesius, which
means sky blue. Caesium should be considered highly toxic. Some of the
radioisotopes are even more toxic.</ar>
<ar><k>calcium</k>
calcium
Symbol: Ca
Atomic number: 20
Atomic weight: 40.08
Soft grey metallic element belonging to group 2 of the periodic table.
Used a reducing agent in the extraction of thorium, zirconium and
uranium. Essential element for living organisms.</ar>
<ar><k>californium</k>
californium
Symbol: Cf
Atomic number: 98
Atomic weight: (249)
Radioactive metallic transuranic element. Belongs to actinoid series.
Cf-251 has a half life of about 700 years. Nine isotopes are known.
Cf-252 is an intense {neutron} source, which makes it an intense
{neutron} source and gives it a use in {neutron} activation analysis
and a possible use as a radiation source in medicine. First produced
by Glenn T. Seaborg and associates in 1950.</ar>
<ar><k>carbon</k>
carbon
Symbol: C
Atomic number: 6
Atomic weight: 12.01115
Carbon is a member of group 14 of the periodic table. It has three
allotropic forms of it, diamonds, graphite and fullerite. Carbon-14
is commonly used in radioactive dating. Carbon occurs in all organic life
and is the basis of organic chemistry. Carbon has the interesting chemical
property of being able to bond with itself, and a wide variety of other
elements.</ar>
<ar><k>cerium</k>
cerium
Symbol: Ce
Atomic number: 58
Atomic weight: 140.12
Silvery metallic element, belongs to the lanthanoids. Four natural
isotopes exist, and fifteen radioactive isotopes have been identified.
Used in some rare-earth alloys. The oxidized form is used in the glass
industry. Discovered by Martin .H. Klaproth in 1803.</ar>
<ar><k>chlorine</k>
chlorine
Symbol: Cl
Atomic number: 17
Atomic weight: 35.453
Halogen element. Poisonous greenish-yellow gas. Occurs widely in nature as
sodium chloride in seawater. Reacts directly with many elements and
compounds, strong oxidizing agent. Discovered by Karl Scheele in 1774.
Humphrey David confirmed it as an element in 1810.</ar>
<ar><k>chromium</k>
chromium
Symbol: Cr
Atomic number: 24
Atomic weight: 51.996
Hard silvery transition element. Used in decorative electroplating.
Discovered in 1797 by Vauquelin.</ar>
<ar><k>cobalt</k>
cobalt
Symbol: Co
Atomic number: 27
Atomic weight: 58.993
Light grey transition element. Some meteorites contain small amounts of
metallic cobalt. Generally alloyed for use. Mammals require small amounts
of cobalt salts. Cobalt-60, an artificially produced radioactive isotope
of Cobalt is an important radioactive tracer and cancer-treatment agent.
Discovered by G. Brandt in 1737.</ar>
<ar><k>columbium</k>
columbium
The original name for {niobium}.</ar>
<ar><k>copper</k>
copper
Symbol: Cu
Atomic number: 29
Atomic weight: 63.54
Red-brown transition element. Known by the Romans as 'cuprum.' Extracted
and used for thousands of years. Malleable, ductile and an excellent
conductor of heat and electricity. When in moist conditions, a greenish
layer forms on the outside.</ar>
<ar><k>cuprum</k>
cuprum
Roman name for {copper}.</ar>
<ar><k>curium</k>
curium
Symbol: Cm
Atomic number: 96
Atomic weight: (247)
Radioactive metallic transuranic element. Belongs to actinoid series.
Nine known isotopes, Cm-247 has a half-life of 1.64*10^7 years. First
identified by Glenn T. Seaborg and associates in 1944, first produced by
L.B. Werner and I. Perlman in 1947 by bombarding americium-241 with
{neutron}s. Named for Marie Curie.</ar>
<ar><k>deuterium</k>
deuterium
Symbol: D
Atomic Weight: 2
A {hydrogen} atom which has but one proton and {neutron}. Deuterium makes up
about 0.015% of all natural hydrogen. Chemical properties are like that of
normal {hydrogen}, though somewhat slower.</ar>
<ar><k>dubnium</k>
dubnium
Symbol: Db
Competing name for {unnilquadium}, the 104th element, proposed by the
IUPAC.</ar>
<ar><k>dysprosium</k>
dysprosium
Symbol: Dy
Atomic number: 66
Atomic weight: 162.50
Metallic with a bright silvery-white lustre. Dysprosium belongs to the
lanthanoids. It is relatively stable in air at room temperatures, it will
however dissolve in mineral acids, evolving hydrogen. It is found in
from rare-earth minerals. There are seven natural isotopes of dysprosium,
and eight radioisotopes, Dy-154 being the most stable with a half-life of
3*10^6 years. Dysprosium is used as a neutron absorber in nuclear fission
reactions, and in compact disks. It was discovered by Paul Emile Lecoq de
Boisbaudran in 1886 in France. Its name comes from the Greek word
dysprositos, which means hard to obtain.</ar>
<ar><k>einsteinium</k>
einsteinium
Symbol: Es
Atomic number: 99
Atomic weight: (254)
Appearance is unknown, however it is most probably metallic and silver
or gray in color. Radioactive metallic transuranic element belonging to the
actinoids. Es-254 has the longest half-life of the eleven known isotopes at
270 days. First identified by Albert Ghiorso and associates in the debris of
the 1952 hydrogen bomb explosion. In 1961 the first microgram quantities of
Es-232 were separated. While einsteinium never exists naturally, if a
sufficient amount was assembled, it would pose a radiation hazard.</ar>
<ar><k>erbium</k>
erbium
Symbol: Er
Atomic number: 68
Atomic weight: 167.26
Soft silvery metallic element which belongs to the lanthanoids. Six
natural isotopes that are stable. Twelve artificial isotopes are known.
Used in nuclear technology as a neutron absorber. It is being investigated
for other possible uses. Discovered by Carl G. Mosander in 1843.</ar>
<ar><k>europium</k>
europium
Symbol: Eu
Atomic number: 63
Atomic weight: 151.25
Soft silvery metallic element belonging to the lanthanoids. Eu-151 and
Eu-153 are the only two stable isotopes, both of which are {neutron}
absorbers. Discovered in 1889 by Sir William Crookes.</ar>
<ar><k>fermium</k>
fermium
Symbol: Fm
Atomic number: 100
Atomic weight: (253)
Radioactive metallic transuranic element, belongs to the actinoids. Ten
known isotopes, most stable is Fm-257 with a half-life of 10 days. First
identified by Albert Ghiorso and associates in the debris of the first
hydrogen-bomb explosion in 1952.</ar>
<ar><k>fluorine</k>
fluorine
Symbol: F
Atomic number: 9
Atomic weight: 18.9984
A poisonous pale yellow gaseous element belonging to group 17 of the
periodic table (The halogens). It is the most chemically reactive and
electronegative element. It is highly dangerous, causing severe chemical
burns on contact with flesh. Fluorine was identified by Scheele in 1771
and first isolated by Moissan in 1886.</ar>
<ar><k>francium</k>
francium
Symbol: Fr
Atomic number: 87
Atomic weight: (223)
Radioactive element, belongs to group 1 of the periodic table. Found in
uranium and thorium ores. The 22 known isotopes are all radioactive, with
the most stable being Fr-223. Its existence was confirmed in 1939 by
Marguerite Perey.</ar>
<ar><k>gadolinium</k>
gadolinium
Symbol: Gd
Atomic number: 64
Atomic weight: 157.25
Soft silvery metallic element belonging to the lanthanoids. Seven natural,
stable isotopes are known in addition to eleven artificial isotopes.
Gd-155 and Gd-157 and the best neutron absorbers of all elements.
Gadolinium compounds are used in electronics. Discovered by J.C.G Marignac
in 1880.</ar>
<ar><k>gallium</k>
gallium
Symbol: Ga
Atomic number: 31
Atomic weight: 69.72
Soft silvery metallic element, belongs to group 13 of the periodic table.
The two stable isotopes are Ga-69 and Ga-71. Eight radioactive isotopes
are known, all having short half-lives. Gallium Arsenide is used as a
semiconductor. Corrodes most other metals by diffusing into their lattice.
First identified by Francois Lecoq de Boisbaudran in 1875.</ar>
<ar><k>germanium</k>
germanium
Symbol: Ge
Atomic number: 32
Atomic weight: 72.59
Lustrous hard metalloid element, belongs to group 14 of the periodic
table. Forms a large number of organometallic compounds. Predicted by
Mendeleev in 1871, it was actually found in 1886 by Winkler.</ar>
<ar><k>gold</k>
gold
Symbol: Au
Atomic number: 79
Atomic weight: 196.96655
Gold is gold colored. It is the most malleable and ductile metal known.
There is only one stable isotope of gold, and five radioisotopes of gold,
Au-195 being the most stable with a half-life of 186 days. Gold is used
as a monetary standard, in jewelry, dentistry, electronics. Au-198 is used
in treating cancer and some other medical conditions. Gold has been known
to exist as far back as 2600 BC. Gold comes from the Anglo-Saxon word gold.
Its symbol, Au, comes from the Latin word aurum, which means gold. Gold is
not particularly toxic, however it is known to cause damage to the liver
and kidneys in some.</ar>
<ar><k>hafnium</k>
hafnium
Symbol: Hf
Atomic number: 72
Atomic weight: 178.49
Silvery lustrous metallic transition element. Used in tungsten alloys in
filaments and electrodes, also acts as a neutron absorber. First reported
by Urbain in 1911, existence was finally established in 1923 by D. Coster,
G.C. de Hevesy in 1923.</ar>
<ar><k>hahnium</k>
hahnium
Symbol: Ha
Competing name for {unnilpentium}, the 105th element, proposed by the
American Chemical Society. Also a competing name for {unniloctium}, the
108th element, proposed by the IUPAC. Both were chosen in honor of German
researcher, Otto Hahn.</ar>
<ar><k>hassium</k>
hassium
Competing name for {unniloctium}, the 108th element, proposed by its
German discoverers and supported by the American Chemical Society.</ar>
<ar><k>helium</k>
helium
Symbol: He
Atomic number: 2
Atomic weight: 4.0026
Colourless, odourless gaseous nonmetallic element. Belongs to group 18 of
the periodic table. Lowest boiling point of all elements and can only be
solidified under pressure. Chemically inert, no known compounds.
Discovered in the solar spectrum in 1868 by Lockyer.</ar>
<ar><k>holmium</k>
holmium
Symbol: Ho
Atomic number: 67
Atomic weight: 167.26
Relatively soft and malleable silvery-white metallic element, which is stable
in dry air at room temperature. It oxidizes in moist air and at high
temperatures. It belongs to the lanthanoids. A rare-earth metal, it is found
in the minerals monazite and gadolinite. It possesses unusual magnetic
properties. One natural isotope, Ho-165 exists, six radioisotopes exist, the
most stable being Ho-163 with a half-life of 4570 years. Holmium is used in
some metal alloys, it is also said to stimulate the metabolism. Discovered by
Per Theodor Cleve and J.L. Soret in Switzerland in 1879. The name homium comes
from the Greek word Holmia which means Sweden. While all holmium compounds
should be considered highly toxic, initial evidence seems to indicate that
they do not pose much danger. The metal's dust however, is a fire hazard.</ar>
<ar><k>hydrogen</k>
hydrogen
Symbol: H
Atomic number: 1
Atomic weight: 1.0079
Colourless, odourless gaseous chemical element. Lightest and most
abundant element in the universe. Present in water and in all organic
compounds. Chemically reacts with most elements. Discovered by Henry
Cavendish in 1776.</ar>
<ar><k>indium</k>
indium
Symbol: In
Atomic number: 49
Atomic weight: 114.82
Soft silvery element belonging to group 13 of the periodic table. The most
common natural isotope is In-115, which has a half-life of 6*10^4 years.
Five other radioisotopes exist. Discovered in 1863 by Reich and Richter.</ar>
<ar><k>iodine</k>
iodine
Symbol: I
Atomic number: 53
Atomic weight: 126.904
Dark violet nonmetallic element, belongs to group 17 of the periodic
table. Insoluble in water. Required as a trace element for living
organisms. One stable isotope, I-127 exists, in addition to fourteen
radioactive isotopes. Chemically the least reactive of the halogens, and
the most electropositive metallic halogen. Discovered in 1812 by Courtois.</ar>
<ar><k>iridium</k>
iridium
Symbol: Ir
Atomic number: 77
Atomic weight: 192.217
Very hard and brittle, silvery metallic transition element. It has a
yellowish cast to it. Salts of iridium are highly colored. It is the
most corrosion resistant metal known, not attacked by any acid, but is
attacked by molten salts. There are two natural isotopes of iridium, and
4 radioisotopes, the most stable being Ir-192 with a half-life of 73.83
days. Ir-192 decays into {platinum}, while the other radioisotopes decay
into {osmium}. Iridium is used in high temperature apparatus, electrical
contacts, and as a hardening agent for platinum. Discovered in 1803 by
Smithson Tennant in England. The name comes from the Greek word iris, which
means rainbow. Iridium metal is generally non-toxic due to its relative
unreactivity, but iridium compounds should be considered highly toxic.</ar>
<ar><k>iron</k>
iron
Symbol: Fe
Atomic number: 26
Atomic weight: 55.847
Silvery malleable and ductile metallic transition element. Has nine
isotopes and is the fourth most abundant element in the earth's crust.
Required by living organisms as a trace element (used in hemoglobin in
humans.) Quite reactive, oxidizes in moist air, displaces hydrogen from
dilute acids and combines with nonmetallic elements.</ar>
<ar><k>IUPAC</k>
IUPAC
The International Union of Pure and Applied Chemistry.</ar>
<ar><k>joliotium</k>
joliotium
Symbol: Jl
Competing name for {unnilpentium}, the 105th element, proposed by the
IUPAC.</ar>
<ar><k>krypton</k>
krypton
Symbol: Kr
Atomic number: 36
Atomic weight: 83.80
Colorless gaseous element, belongs to the noble gases. Occurs in the air,
0.0001% by volume. It can be extracted from liquid air by fractional
distillation. Generally not isolated, but used with other inert gases in
fluorescent lamps. Five natural isotopes, and five radioactive isotopes.
Kr-85, the most stable radioactive isotope, has a half-life of 10.76
years and is produced in fission reactors. Practically inert, though known
to form compounds with {fluorine}.</ar>
<ar><k>kurchatovium</k>
kurchatovium
Symbol: Ku
Competing name for {unnilquadium}, the 104th element, proposed by Russian
scientists.</ar>
<ar><k>lanthanum</k>
lanthanum
Symbol: La
Atomic number: 57
Atomic weight: 138.9055
(From the Greek word lanthanein, to line hidden) Silvery metallic element
belonging to group 3 of the periodic table and oft considered to be one of
the lanthanoids. Found in some rare-earth minerals. Twenty-five natural
isotopes exist. La-139 which is stable, and La-138 which has a half-life
of 10^10 to 10^15 years. The other twenty-three isotopes are radioactive.
It resembles the lanthanoids chemically. Lanthanum has a low to moderate
level of toxicity, and should be handled with care. Discovered in 1839 by
C.G. Mosander.</ar>
<ar><k>lawrencium</k>
lawrencium
Symbol: Lr
Atomic number: 103
Atomic weight: (262)
Appearance unknown, however it is most likely silvery-white or grey
and metallic. Lawrencium is a synthetic rare-earth metal. There are
eight known radioisotopes, the most stable being Lr-262 with a half-life
of 3.6 hours. Due to the short half-life of lawrencium, and its
radioactivity, there are no known uses for it. Identified by Albert Ghiorso
in 1961 at Berkeley. It was produced by bombarding californium with boron
ions. The name is temporary {IUPAC} nomenclature, the origin of the name
comes from Ernest O. Lawrence, the inventor of the cyclotron. If sufficient
amounts of lawrencium were produced, it would pose a radiation hazard.</ar>
<ar><k>lead</k>
lead
Symbol: Pb
Atomic number: 82
Atomic weight: 207.19
Heavy dull grey ductile metallic element, belongs to group 14. Used in
building construction, lead-place accumulators, bullets and shot, and is
part of solder, pewter, bearing metals, type metals and fusible alloys.</ar>
<ar><k>lithium</k>
lithium
Symbol: Li
Atomic number: 3
Atomic weight: 6.939
Socket silvery metal. First member of group 1 of the periodic table.
Lithium salts are used in psychomedicine.</ar>
<ar><k>lutetium</k>
lutetium
Symbol: Lu
Atomic number: 71
Atomic weight: 194.967
Silvery-white rare-earth metal which is relatively stable in air. It
happens to be the most expensive rare-earth metal. Its found with almost
all rare-earth metals, but is very difficult to separate from other
elements. Least abundant of all natural elements. Used in metal alloys,
and as a catalyst in various processes. There are two natural, stable
isotopes, and seven radioisotopes, the most stable being Lu-174 with a
half-life of 3.3 years. The separation of lutetium from {ytterbium} was
described by Georges Urbain in 1907. It was discovered at approximately
the same time by Carl Auer von Welsbach. The name comes from the Greek
word lutetia which means Paris.</ar>
<ar><k>magnesium</k>
magnesium
Symbol: Mg
Atomic number: 12
Atomic weight: 24.312
Silvery metallic element belonging to group 2 of the periodic table
(alkaline-earth metals). It is essential for living organisms, and is used
in a number of light alloys. Chemically very reactive, it forms a
protective oxide coating when exposed to air and burns with an intense
white flame. It also reacts with sulphur, nitrogen and the halogens. First
isolated by Bussy in 1828.</ar>
<ar><k>manganese</k>
manganese
Symbol: Mn
Atomic number: 25
Atomic weight: 54.938
Grey brittle metallic transition element. Rather electropositive, combines
with some non-metals when heated. Discovered in 1774 by Scheele.</ar>
<ar><k>meitnerium</k>
meitnerium
Symbol: Mt
Atomic number: 109
Atomic weight: (266)
Half-life of approximately 5ms. The creation of this element demonstrated
that fusion techniques could indeed be used to make new, heavy nuclei.
Made and identified by physicists of the Heavy Ion Research Laboratory,
Darmstadt, West Germany in 1982. Named in honor of Lise Meitner the
Austrian physicist.</ar>
<ar><k>mendelevium</k>
mendelevium
Symbol: Md
Atomic number: 101
Atomic weight: (256)
Radioactive metallic transuranic element. Belongs to the actinoid series.
Only known isotope, Md-256 has a half-life of 1.3 hours. First identified
by Glenn T. Seaborg, Albert Ghiorso and associates in 1955. Alternative
name {unnilunium} has been proposed. Named after the 'inventor' of the
periodic table, Dmitri Mendeleev.</ar>
<ar><k>mercury</k>
mercury
Symbol: Hg
Atomic number: 80
Atomic weight: 200.59
Heavy silvery liquid metallic element, belongs to the zinc group. Used in
thermometers, barometers and other scientific apparatus. Less reactive
than zinc and cadmium, does not displace hydrogen from acids. Forms a
number of complexes and organomercury compounds.</ar>
<ar><k>molybdenum</k>
molybdenum
Symbol: Mo
Atomic number: 42
Atomic weight: 95.94
Silvery-white, hard metallic transition element. It is chemically
unreactive and is not affected by most acids. It oxidizes at high
temperatures. There are seven natural isotopes, and four radioisotopes,
Mo-93 being the most stable with a half-life of 3500 years. Molybdenum
is used in almost all high-strength steels, it has nuclear applications,
and is a catalyst in petroleum refining. Discovered in 1778 by Carl
Welhelm Scheele of Sweden. Impure metal was prepared in 1782 by Peter
Jacob Hjelm. The name comes from the Greek word molybdos which means lead.
Trace amounts of molybdenum are required for all known forms of life.
All molybdenum compounds should be considered highly toxic, and will
also cause severe birth defects.</ar>
<ar><k>neodymium</k>
neodymium
Symbol: Nd
Atomic number: 60
Atomic weight: 144.24
Soft bright silvery metallic element, belongs to the lanthanoids. Seven natural
isotopes, Nd-144 being the only radioactive one with a half-life of 10^10
to 10^15 years. Six artificial radioisotopes have been produced. The
metal is used in glass works to color class a shade of violet-purple and
make it dichroic. One of the more reactive rare-earth metals, quickly reacts
with air. Used in some rare-earth alloys. Neodymium is used to color
the glass used in welder's glasses. Neodymium is also used in very
powerful, permanent magnets (Nd2Fe14B). Discovered by Carl F. Auer von
Welsbach in Austria in 1885 by separating didymium into its elemental
components {praseodymium} and neodymium. The name comes from the Greek words
&quot;neos didymos&quot; which means &quot;new twin&quot;. Neodymium should be considered
highly toxic, however evidence would seem to show that it acts as little
more than a skin and eye irritant. The dust however, presents a fire and
explosion hazard.</ar>
<ar><k>neon</k>
neon
Symbol: Ne
Atomic number: 10
Atomic weight: 20.183
Colourless gaseous element of group 18 on the periodic table (noble
gases). Neon occurs in the atmosphere, and comprises 0.0018% of the volume
of the atmosphere. It has a distinct reddish glow when used in discharge
tubes and neon based lamps. It forms almost no chemical compounds. Neon
was discovered in 1898 by Sir William Ramsey and M.W. Travers.</ar>
<ar><k>neptunium</k>
neptunium
Symbol: Np
Atomic number: 93
Atomic weight: (237)
Radioactive metallic transuranic element, belongs to the actinoids.
Np-237, the most stable isotope, has a half-life of 2.2*10^6 years and is
a by product of nuclear reactors. The other known isotopes have mass
numbers 229 through 236, and 238 through 241. Np-236 has a half-life of
5*10^3 years. First produced by Edwin M. McMillan and P.H. Abelson in
1940.</ar>
<ar><k>neutron</k>
neutron
Weight: 1.6749286*10^-27kg
A neutral hadron that is stable in the atomic nucleus but decays into a
protron, an electron and an antineutrino with a mean life of 12 minutes
outside the nucleus. Neutrons exist in all atomic nuclei except normal
hydrogen. Reported in 1932 by James Chadwick.</ar>
<ar><k>nickel</k>
nickel
Symbol: Ni
Atomic number: 28
Atomic weight: 58.71
Malleable ductile silvery metallic transition element. Discovered by A.F.
Cronstedt in 1751.</ar>
<ar><k>nielsbohrium</k>
nielsbohrium
Competing name for {unnilseptium}, the 107th element, proposed by its West
German discoverers and supported by the American Chemical Society. The
name was chosen in honor of physicist, Niels Bohr.</ar>
<ar><k>niobium</k>
niobium
Symbol: Nb
Atomic number: 41
Atomic weight: 92.906
Soft, ductile grey-blue metallic transition element. Used in special
steels and in welded joints to increase strength. Combines with halogens
and oxidizes in air at 200 degrees celsius. Discovered by Charles Hatchett
in 1801 and isolated by Blomstrand in 1864. Called {columbium} originally.</ar>
<ar><k>nitrogen</k>
nitrogen
Symbol: N
Atomic number: 7
Atomic weight: 14.0067
Colourless, gaseous element which belongs to group 15 of the periodic
table. Constitutes ~78% of the atmosphere and is an essential part of the
ecosystem. Nitrogen for industrial purposes is acquired by the fractional
distillation of liquid air. Chemically inactive, reactive generally only
at high temperatures or in electrical discharges. It was discovered in
1772 by D. Rutherford.</ar>
<ar><k>nobelium</k>
nobelium
Symbol: No
Atomic number: 102
Atomic weight: (254)
Radioactive metallic transuranic element, belongs to the actinoids. Seven
known isotopes exist, the most stable being No-254 with a half-life of 255
seconds. First identified with certainty by Albert Ghiorso and Glenn T.
Seaborg in 1966. {Unnilbium} has been proposed as an alternative name.</ar>
<ar><k>osmium</k>
osmium
Symbol: Os
Atomic number: 76
Atomic weight: 190.2
Hard blue-white metallic transition element. Found with platinum and used
in some alloys with platinum and iridium.</ar>
<ar><k>oxygen</k>
oxygen
Symbol: O
Atomic number: 8
Atomic weight: 15.9994
A colourless, odourless gaseous element belonging to group 16 of the
periodic table. It is the most abundant element present in the earth's
crust. It also makes up 20.8% of the Earth's atmosphere. For industrial
purposes, it is separated from liquid air by fractional distillation. It
is used in high temperature welding, and in breathing. It commonly comes
in the form of Oxygen, but is found as Ozone in the upper atmosphere. It
was discovered by Priestley in 1774.</ar>
<ar><k>palladium</k>
palladium
Symbol: Pd
Atomic number: 46
Atomic weight: 106.4
Soft white ductile transition element. Found with some copper and nickel
ores. Does not react with oxygen at normal temperatures. Dissolves slowly
in hydrochloric acid. Discovered in 1803 by W.H. Wollaston.</ar>
<ar><k>phosphorus</k>
phosphorus
Symbol: P
Atomic number: 15
Atomic weight: 30.9738
Non-metallic element belonging to group 15 of the periodic table. Has a
multiple allotropic forms. Essential element for living organisms. It was
discovered by Brandt in 1669.</ar>
<ar><k>platinum</k>
platinum
Symbol: Pt
Atomic number: 78
Atomic weight: 195.078
Attractive greyish-white metal. When pure, it is malleable and ductile.
Does not oxidize in air, insoluble in hydrochloric and nitric acid.
Corroded by halogens, cyandies, sulphur and alkalis. {Hydrogen} and
{oxygen} react explosively in the presence of platinum. There are six
stable isotopes and three radioisotopes, the most stable being Pt-193
with a half-life of 60 years. Platinum is used in jewelry, laboratory
equipment, electrical contacts, dentistry, and anti-pollution devices in
cars. PtCl2(NH3)2 is used to treat some forms of cancer. Platinum-{cobalt}
alloys have magnetic properties. It is also used in the definition of
the Standard Hydrogen Electrode. Discovered by Antonio de Ulloa in South
America in 1735. The name comes from the Spanish word platina which means
silver. Platinum metal is generally not a health concern due to its
unreactivity, however platinum compounds should be considered highly
toxic.</ar>
<ar><k>plutonium</k>
plutonium
Symbol: Pu
Atomic number: 94
Atomic weight: (242)
Dense silvery radioactive metallic transuranic element, belongs to the
actinoids. Pu-244 is the most stable isotope with a half-life of 7.6*10^7
years. Thirteen isotopes are known. Pu-239 is the most important, it
undergoes nuclear fission with slow neutrons and is hence important to
nuclear weapons and reactors. Plutonium production is monitored down to
the gram to prevent military misuse. First produced by Gleen T. Seaborg,
Edwin M. McMillan, J.W. Kennedy and A.C. Wahl in 1940.</ar>
<ar><k>polonium</k>
polonium
Symbol: Po
Atomic number: 84
Atomic weight: (210)
Rare radioactive metallic element, belongs to group 16 of the periodic
table. Over 30 known isotopes exist, the most of all elements. Po-209 has
a half-life of 103 years. Possible uses in heating spacecraft. Discovered
by Marie Curie in 1898 in a sample of pitchblende.</ar>
<ar><k>potassium</k>
potassium
Symbol: K
Atomic number: 19
Atomic weight: 39.0983
Soft silvery metallic element belonging to group 1 of the periodic table
(alkali metals). Occurs naturally in seawater and a many minerals. Highly
reactive, chemically, it resembles sodium in its behavior and compounds.
Discovered by Sir Humphry Davy in 1807.</ar>
<ar><k>praseodymium</k>
praseodymium
Symbol: Pr
Atomic number: 59
Atomic weight: 140.907
Soft silvery metallic element, belongs to the lanthanoids. Only natural
isotope is Pr-141 which is not radioactive.  Fourteen radioactive isotopes
have been artificially produced. Used in rare-earth alloys. Discovered in
1885 by C.A. von Welsbach.</ar>
<ar><k>promethium</k>
promethium
Symbol: Pm
Atomic number: 61
Atomic weight: (147)
Soft silvery metallic element, belongs to the lanthanoids. Pm-147, the
only natural isotope, is radioactive and has a half-life of 252 years.
Eighteen radioisotopes have been produced, but all have very short
half-lives. Found only in nuclear decay waste. Pm-147 is of interest as a
beta-decay source, however Pm-146 and Pm-148 have to be removed from it
first, as they generate gamma radiation. Discovered by J.A. Marinsky,
L.E. Glendenin and C.D. Coryell in 1947.</ar>
<ar><k>protactinium</k>
protactinium
Symbol: Pa
Atomic number: 91
Atomic weight: (231)
Radioactive metallic element, belongs to the actinoids. The most stable
isotope, Pa-231 has a half-life of 2.43*10^4 years. At least 10 other
radioactive isotopes are known. No practical applications are known.
Discovered in 1917 by Lise Meitner and Otto Hahn.</ar>
<ar><k>radium</k>
radium
Symbol: Ra
Atomic number: 88
Atomic weight: (226)
Radioactive metallic transuranic element, belongs to group 2 of the
periodic table. Most stable isotope, Ra-226 has a half-life of 1602 years,
which decays into radon. Isolated from pitchblende in 1898 Marie and
Pierre Curie.</ar>
<ar><k>radon</k>
radon
Symbol: Rn
Atomic number: 86
Atomic weight: (222)
Colorless radioactive gaseous element, belongs to the noble gases. Of the
twenty known isotopes, the most stable is Rn-222 with a half-life of 3.8 days.
Formed by the radioactive decay of {Radium}-226. Radon itself decays into
{polonium}. Used in radiotherapy. As a noble gas, it is effectively inert,
though radon fluoride has been synthesized. First isolated in 1908 by Ramsey
and Gray.</ar>
<ar><k>rhenium</k>
rhenium
Symbol: Re
Atomic number: 75
Atomic weight: 186.2
Silvery-white metallic transition element. Obtained as a by-product of
molybdenum refinement. Rhenium-molybdenum alloys are superconducting.</ar>
<ar><k>rhodium</k>
rhodium
Symbol: Rh
Atomic number: 45
Atomic weight: 102.905
Silvery white metallic transition element. Found with platinum and used in
some platinum alloys. Not attacked by acids, dissolves only in aqua regia.
Discovered in 1803 by W.H. Wollaston.</ar>
<ar><k>rubidium</k>
rubidium
Symbol: Rb
Atomic number: 37
Atomic weight: 85.47
Soft silvery metallic element, belongs to group 1 of the periodic table.
Rb-97, the naturally occurring isotope, is radioactive. It is highly
reactive, with properties similar to other elements in group 1, like
igniting spontaneously in air. Discovered spectroscopically in 1861 by W.
Bunsen and G.R. Kirchoff.</ar>
<ar><k>ruthenium</k>
ruthenium
Symbol: Ru
Atomic number: 44
Atomic weight: 101.07
Hard white metallic transition element. Found with platinum, used as a
catalyst in some platinum alloys. Dissolves in fused alkalis, and is not
attacked by acids. Reacts with halogens and oxygen at high temperatures.
Isolated in 1844 by K.K. Klaus.</ar>
<ar><k>rutherfordium</k>
rutherfordium
Symbol: Rf
Competing name for {unnilquadium}, the 104th element, proposed by the
American Chemical Society.</ar>
<ar><k>samarium</k>
samarium
Symbol: Sm
Atomic number: 62
Atomic weight: 150.35
Soft silvery metallic element, belongs to the lanthanoids. Seven natural
isotopes, Sm-147 is the only radioisotope, and has a half-life of
2.5*10^11 years. Used for making special alloys needed in the production
of nuclear reactors. Also used as a neutron absorber. Small quantities of
samarium oxide is used in special optical glasses. The largest use of the
element is its ferromagnetic alloy which produces permanent magnets that
are five times stronger than magnets produced by any other material.
Discovered by Francois Lecoq de Boisbaudran in 1879.</ar>
<ar><k>scandium</k>
scandium
Symbol: Sc
Atomic number: 21
Atomic weight: 44.956
Rare soft silvery metallic element belonging to group 3 of the periodic
table. There are ten isotopes, nine of which are radioactive and have
short half-lives. Predicted in 1869 by Mendeleev, isolated by Nilson in
1879.</ar>
<ar><k>seaborgium</k>
seaborgium
Name proposed for the 106th element ({unnilhexium}) by the American
Chemical Society in honor of Gleen T. Seaborg, an American nuclear
physicist and Nobel prize winner.</ar>
<ar><k>selenium</k>
selenium
Symbol: Se
Atomic number: 34
Atomic weight: 78.96
Metalloid element, belongs to group 16 of the periodic table. Multiple
allotropic forms exist. Chemically resembles sulphur. Discovered in 1817
by Jons J. Berzelius.</ar>
<ar><k>silicon</k>
silicon
Symbol: Si
Atomic number: 14
Atomic weight: 28.086
Metalloid element belonging to group 14 of the periodic table. It is the
second most abundant element in the Earth's crust, making up 25.7% of it
by weight. Chemically less reactive than carbon. First identified by
Lavoisier in 1787 and first isolated in 1823 by Berzelius.</ar>
<ar><k>silver</k>
silver
Symbol: Ag
Atomic number: 47
Atomic weight: 107.870
White lustrous soft metallic transition element. Found in both its
elemental form and in minerals. Used in jewellery, tableware and so on.
Less reactive than silver, chemically.</ar>
<ar><k>sodium</k>
sodium
Symbol: Na
Atomic number: 11
Atomic weight: 22.9898
Soft silvery reactive element belonging to group 1 of the periodic table
(alkali metals). It is highly reactive, oxidizing in air and reacting
violently with water, forcing it to be kept under oil. It was first
isolated by Humphrey Davy in 1807.</ar>
<ar><k>strontium</k>
strontium
Symbol: Sr
Atomic number: 38
Atomic weight: 87.62
Soft yellowish metallic element, belongs to group 2 of the periodic
table. Highly reactive chemically. Sr-90 is present in radioactive fallout
and has a half-life of 28 years. Discovered in 1798 by Klaproth and Hope,
isolated in 1808 by Humphry Davy.</ar>
<ar><k>sulphur</k>
sulphur
Symbol: S
Atomic number: 16
Atomic weight: 32.064
Yellow, nonmetallic element belonging to group 16 of the periodic table.
It is an essential element in living organisms, needed in the amino acids
cysteine and methionine, and hence in many proteins. Absorbed by plants
from the soil as sulphate ion.</ar>
<ar><k>tantalum</k>
tantalum
Symbol: Ta
Atomic number: 73
Atomic weight: 180.948
Heavy blue-grey metallic transition element. Ta-181 is a stable isotope,
and Ta-180 is a radioactive isotope, with a half-life in excess of 10^7
years. Used in surgery as it is unreactive. Forms a passive oxide layer in
air. Identified in 1802 by Ekeberg and isolated in 1820 by Jons J.
Berzelius.</ar>
<ar><k>technetium</k>
technetium
Symbol: Tc
Atomic number: 43
Atomic weight: (98)
Radioactive metallic transition element. Can be detected in some stars and
the fission products of uranium. First made by Perrier and Segre by
bombarding molybdenum with deutrons, giving them Tc-97. Tc-99 is the most
stable isotope with a half-life of 2.6*10^6 years. Sixteen isotopes are
known. Organic technetium compounds are used in bone imaging. Chemical
properties are intermediate between rhenium and manganese.</ar>
<ar><k>tellurium</k>
tellurium
Symbol: Te
Atomic number: 52
Atomic weight: 127.60
Silvery metalloid element of group 16. Eight natural isotopes, nine
radioactive isotopes. Used in semiconductors and to a degree in some
steels. Chemistry is similar to {sulphur}. Discovered in 1782 by Franz
Miller.</ar>
<ar><k>terbium</k>
terbium
Symbol: Tb
Atomic number: 65
Atomic weight: 158.924
Silvery metallic element belonging to the lanthanoids. Tb-159 is the only
stable isotope, there are seventeen artificial isotopes. Discovered by
G.G. Mosander in 1843.</ar>
<ar><k>thallium</k>
thallium
Symbol: Tl
Atomic number: 81
Atomic weight: 204.3833
Pure, unreacted thallium appears silvery-white and exhibits a metallic
lustre. Upon reacting with air, it begins to turn bluish-grey and looks
like lead. It is very malleable, and can be cut with a knife. There are
two stable isotopes, and four radioisotopes, Tl-204 being the most stable
with a half-life of 3.78 years. Thallium sulphate was used as a rodenticide.
Thallium sulphine's conductivity changes with exposure to infrared light,
this gives it a use in infrared detectors. Discovered by Sir William Crookes
via spectroscopy. Its name comes from the Greek word thallos, which means
green twig. Thallium and its compounds are toxic and can cause cancer.</ar>
<ar><k>thorium</k>
thorium
Symbol: Th
Atomic number: 90
Atomic weight: 232.038
Grey radioactive metallic element. Belongs to actinoids. Found in monazite sand
in Brazil, India and the US.  Thorium-232 has a half-life of 1.39x10^10 years.
Can be used as a nuclear fuel for breeder reactors. Thorium-232 captures slow
{neutron}s and breeds uranium-233. Discovered by Jons J. Berzelius in
1829.</ar>
<ar><k>thulium</k>
thulium
Symbol: Tm
Atomic number: 69
Atomic weight: 168.934
Soft grey metallic element that belongs to the lanthanoids. One natural
isotope exists, Tm-169, and seventeen artificial isotopes have been
produced. No known uses for the element. Discovered in 1879 by Per Theodor
Cleve.</ar>
<ar><k>tin</k>
tin
Symbol: Sn
Atomic number: 50
Atomic weight: 118.69
Silvery malleable metallic element belonging to group 14 of the periodic
table. Twenty-six isotopes are known, five of which are radioactive.
Chemically reactive. Combines directly with chlorine and oxygen and
displaces hydrogen from dilute acids.</ar>
<ar><k>titanium</k>
titanium
Symbol: Ti
Atomic number: 22
Atomic weight: 47.90
White metallic transition element. Occurs in numerous minerals. Used in
strong, light corrosion-resistant alloys. Forms a passive oxide coating
when exposed to air. First discovered by Gregor in 1789.</ar>
<ar><k>tungsten</k>
tungsten
Symbol: W
Atomic number: 74
Atomic weight: 183.85
White or grey metallic transition element, formerly called {wolfram}.
Forms a protective oxide in air and can be oxidized at high temperature.
First isolated by Jose and Fausto de Elhuyer in 1783.</ar>
<ar><k>unnilbium</k>
unnilbium
Symbol: Unb
Name proposed by the {IUPAC} to settle the dispute over naming the 102nd
element {nobelium}.</ar>
<ar><k>unnildecium</k>
unnildecium
Symbol: Unn
Atomic number: 110
Atomic weight: (272)?
Half-life of approximately 10ms. Reported in 1994 by German researchers at
Darmstadt, Germany.</ar>
<ar><k>unnilhexium</k>
unnilhexium
Symbol:
Atomic number: 106
Atomic weight: (263)
Half-life of 0.9 +/- 0.2 s. Discovered by the Joint Institute for Nuclear
Research at Dubna (U.S.S.R.) in June of 1974. Its existence was confirmed
by the Lawrence Berkeley Laboratory and Livermore National Laboratory in
September of 1974.</ar>
<ar><k>unniloctium</k>
unniloctium
Symbol: Uno
Atomic number: 108
Atomic weight: (265)
Radioactive transition metal.</ar>
<ar><k>unnilpentium</k>
unnilpentium
Symbol: Unp
Atomic number: 105
Atomic weight: (262)
Radioactive transactinide element. Half-life of 1.6s. Discovered in 1970
by Berkeley researchers. So far, seven isotopes have been discovered.</ar>
<ar><k>unnilquadium</k>
unnilquadium
Symbol: Unq
Atomic number: 104
Atomic weight: (261)
Radioactive transactinide element. Expected to have similar chemical
properties to those displayed by hafnium. Rf-260 was discovered by the
Joint Nuclear Research Institute at Dubna (U.S.S.R.) in 1964. Researchers
at Berkeley discovered Unq-257 and Unq-258 in 1964.</ar>
<ar><k>unnilseptium</k>
unnilseptium
Symbol:
Atomic number: 107
Atomic weight: (262)
Radioactive transition metal. Half-life of approximately 1/500 s.
Discovered by the Joint Institute for Nuclear Research at Dubna (U.S.S.R.)
in 1976. Confirmed by West German physicists at the Heavy Ion Research
Laboratory at Darmstadt.</ar>
<ar><k>unnilunium</k>
unnilunium
Symbol: Unu
Name proposed by the {IUPAC} to settle the dispute over naming the 101st
element {mendelevium}.</ar>
<ar><k>uranium</k>
uranium
Symbol: U
Atomic number: 92
Atomic weight: (231)
White radioactive metallic element belonging to the actinoids. Three
natural isotopes, U-238, U-235 and U-234. Uranium-235 is used as the fuel
for nuclear reactors and weapons. Discovered by Martin H. Klaproth in 1789.</ar>
<ar><k>vanadium</k>
vanadium
Symbol: V
Atomic number: 23
Atomic weight: 50.9415
Soft and ductile, bright white metal. Good resistance to corrosion by
alkalis, sulphuric and hydrochloric acid. It oxidizes readily about
933K. There are two naturally occurring isotopes of vanadium, and 5
radioisotopes, V-49 having the longest half-life at 337 days. Vanadium
has nuclear applications, the foil is used in cladding titanium to steel,
and vanadium-gallium tape is used to produce a superconductive magnet.
Originally discovered by Andres Manuel del Rio of Mexico City in 1801.
His discovery went unheeded, however, and in 1820, Nils Gabriel Sefstron
of Sweden rediscovered it. Metallic vanadium was isolated by Henry Enfield
Roscoe in 1867. The name vanadium comes from {Vanadis}, a goddess of
Scandinavian mythology. Silvery-white metallic transition element.
Vanadium is essential to {ascidian}s. Rats and chickens are also known
to require it. Metal powder is a fire hazard, and vanadium compounds
should be considered highly toxic. May cause lung cancer if inhaled.</ar>
<ar><k>wolfram</k>
wolfram
Original name for {tungsten}.</ar>
<ar><k>xenon</k>
xenon
Symbol: Xe
Atomic number: 54
Atomic weight: 131.30
Colourless, odourless gas belonging to group 18 on the periodic table (the
noble gases.) Nine natural isotopes and seven radioactive isotopes are
known. Xenon was part of the first noble-gas compound synthesized.
Several others involving Xenon have been found since then. Xenon was
discovered by Ramsey and Travers in 1898.</ar>
<ar><k>ytterbium</k>
ytterbium
Symbol: Yb
Atomic number: 70
Atomic weight: 173.04
Silvery metallic element of the lanthanoids. Seven natural isotopes and
ten artificial isotopes are known.  Used in certain steels. Discovered by
J.D.G. Marignac in 1878.</ar>
<ar><k>yttrium</k>
yttrium
Symbol: Y
Atomic number: 39
Atomic weight: 88.905
Silvery-grey metallic element of group 3 on the periodic table. Found in
uranium ores. The only natural isotope is Y-89, there are 14 other
artificial isotopes. Chemically resembles the lanthanoids. Stable in the
air below 400 degrees, celsius. Discovered in 1828 by Friedrich Wohler.</ar>
<ar><k>zinc</k>
zinc
Symbol: Zn
Atomic number: 30
Atomic weight: 65.38
Blue-white metallic element. Occurs in multiple compounds naturally. Five
stable isotopes are six radioactive isotopes have been found. Chemically a
reactive metal, combines with oxygen and other non-metals, reacts with
dilute acids to release hydrogen.</ar>
<ar><k>zirconium</k>
zirconium
Symbol: Zr
Atomic number: 40
Atomic weight: 91.22
Grey-white metallic transition element. Five natural isotopes and six
radioactive isotopes are known. Used in nuclear reactors for a {neutron}
absorber. Discovered in 1789 by Martin Klaproth, isolated in 1824 by
Berzelius.</ar>
</xdxf>