Yttrium Yttrium is a
chemical element with symbol
Y and
atomic number 39. It is a silvery-metallic
transition metal chemically similar to the
lanthanides and it has often been classified as a "
rare earth element". Yttrium is almost always found combined with the lanthanides in
rare earth minerals and is never found in nature as a free element. Its only stable
isotope, 89Y, is also its only naturally occurring isotope. In 1787,
Carl Axel Arrhenius found a new mineral near
Ytterby in Sweden and named it
ytterbite, after the village.
Johan Gadolin discovered yttrium's oxide in Arrhenius' sample in 1789, and
Anders Gustaf Ekeberg named the new oxide
yttria. Elemental yttrium was first isolated in 1828 by
Friedrich Wöhler. Other uses include the production of
electrodes,
electrolytes,
electronic filters,
lasers and
superconductors; various medical applications; and as
traces in various materials to enhance their properties. Yttrium has no known biological role, and exposure to yttrium compounds can cause lung disease in humans.
Zirconium Zirconium is a
chemical element with the symbol
Zr and
atomic number 40. The name of zirconium is taken from the mineral
zircon. Its atomic mass is 91.224. It is a lustrous, gray-white, strong
transition metal that resembles
titanium. Zirconium is mainly used as a
refractory and
opacifier, although minor amounts are used as alloying agent for its strong resistance to corrosion. Zirconium is obtained mainly from the mineral
zircon, which is the most important form of zirconium in use. Zirconium forms a variety of
inorganic and
organometallic compounds such as
zirconium dioxide and
zirconocene dichloride, respectively. Five
isotopes occur naturally, three of which are stable. Zirconium compounds have no biological role.
Niobium Niobium, or
columbium, is a
chemical element with the symbol
Nb and
atomic number 41. It is a soft, grey,
ductile transition metal, which is often found in the
pyrochlore mineral, the main commercial source for niobium, and
columbite. The name comes from
Greek mythology:
Niobe, daughter of
Tantalus. Niobium has physical and chemical properties similar to those of the element
tantalum, and the two are therefore difficult to distinguish. The English chemist
Charles Hatchett reported a new element similar to tantalum in 1801, and named it columbium. In 1809, the English chemist
William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The German chemist
Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. The name of the element was officially adopted as niobium in 1949. It was not until the early 20th century that niobium was first used commercially.
Brazil is the leading producer of niobium and
ferroniobium, an
alloy of niobium and iron. Niobium is used mostly in alloys, the largest part in special
steel such as that used in gas
pipelines. Although alloys contain only a maximum of 0.1%, that small percentage of niobium improves the strength of the steel. The temperature stability of niobium-containing
superalloys is important for its use in
jet and
rocket engines. Niobium is used in various
superconducting materials. These
superconducting alloys, also containing
titanium and
tin, are widely used in the
superconducting magnets of
MRI scanners. Other applications of niobium include its use in welding, nuclear industries, electronics, optics,
numismatics and jewelry. In the last two applications, niobium's low toxicity and ability to be colored by
anodization are particular advantages.
Molybdenum Molybdenum is a
Group 6 chemical element with the symbol
Mo and
atomic number 42. The name is from Neo-Latin
Molybdaenum, from
Ancient Greek , meaning
lead, itself proposed as a
loanword from
Anatolian Luvian and
Lydian languages, since its ores were confused with lead ores. The free element, which is a silvery
metal, has the
sixth-highest melting point of any element. It readily forms hard, stable
carbides, and for this reason it is often used in high-strength
steel alloys. Molybdenum does not occur as a
free metal on Earth, but rather in various
oxidation states in minerals. Industrially, molybdenum
compounds are used in
high-pressure and high-temperature applications, as
pigments and
catalysts. Molybdenum minerals have long been known, but the element was "discovered" (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by
Carl Wilhelm Scheele. The metal was first isolated in 1781 by
Peter Jacob Hjelm. Most molybdenum compounds have low
solubility in water, but the molybdate ion MoO42− is soluble and forms when molybdenum-containing minerals are in contact with
oxygen and water.
Technetium Technetium is the
chemical element with
atomic number 43 and symbol
Tc. It is the lowest
atomic number element without any
stable isotopes; every form of it is
radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature. Naturally occurring technetium occurs as a spontaneous
fission product in
uranium ore or by
neutron capture in
molybdenum ores. The chemical properties of this silvery gray, crystalline
transition metal are intermediate between
rhenium and
manganese. Many of technetium's properties were predicted by
Dmitri Mendeleev before the element was discovered. Mendeleev noted a gap in his
periodic table and gave the undiscovered element the provisional name
ekamanganese (
Em). In 1937 technetium (specifically the
technetium-97 isotope) became the first predominantly artificial element to be produced, hence its name (from the
Greek , meaning "artificial"). Its short-lived
gamma ray-emitting
nuclear isomer—
technetium-99m—is used in
nuclear medicine for a wide variety of diagnostic tests. Technetium-99 is used as a gamma ray-free source of
beta particles. Long-lived
technetium isotopes produced commercially are by-products of
fission of
uranium-235 in
nuclear reactors and are extracted from
nuclear fuel rods. Because no isotope of technetium has a
half-life longer than 4.2 million years (
technetium-98), its detection in
red giants in 1952, which are billions of years old, helped bolster the theory that stars can produce heavier elements.
Ruthenium Ruthenium is a
chemical element with symbol
Ru and
atomic number 44. It is a rare
transition metal belonging to the
platinum group of the
periodic table. Like the other metals of the platinum group, ruthenium is inert to most chemicals. The
Russian scientist
Karl Ernst Claus discovered the element in 1844 and named it after
Ruthenia, the Latin word for
Rus'. Ruthenium usually occurs as a minor component of
platinum ores and its annual production is only about 12
tonnes worldwide. Most ruthenium is used for wear-resistant electrical contacts and the production of thick-film resistors. A minor application of ruthenium is its use in some platinum
alloys.
Rhodium Rhodium is a
chemical element that is a rare, silvery-white, hard, and
chemically inert transition metal and a member of the
platinum group. It has the
chemical symbol Rh and
atomic number 45. It is composed of only one
isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed with similar metals, and never as a chemical compound. It is one of the rarest
precious metals and one of the most costly (
gold has since taken over the top spot of cost per ounce). Rhodium is a so-called
noble metal, resistant to corrosion, found in platinum or nickel ores together with the other members of the
platinum group metals. It was
discovered in 1803 by
William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds, produced after it reacted with the powerful acid mixture
aqua regia. The element's major use (about 80% of world rhodium production) is as one of the
catalysts in the
three-way catalytic converters of automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually
alloyed with
platinum or
palladium and applied in high-temperature and corrosion-resistive coatings.
White gold is often plated with a thin rhodium layer to improve its optical impression while
sterling silver is often rhodium plated for tarnish resistance. Rhodium detectors are used in
nuclear reactors to measure the
neutron flux level.
Palladium Palladium is a
chemical element with the
chemical symbol Pd and an
atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by
William Hyde Wollaston. He named it after the
asteroid Pallas, which was itself named after the
epithet of the
Greek goddess
Athena, acquired by her when she slew
Pallas. Palladium,
platinum,
rhodium,
ruthenium,
iridium and
osmium form a group of elements referred to as the
platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them. The unique properties of palladium and other platinum group metals account for their widespread use. A quarter of all goods manufactured today either contain PGMs or have a significant part in their manufacturing process played by PGMs. Over half of the supply of palladium and its
congener platinum goes into
catalytic converters, which convert up to 90% of harmful gases from auto exhaust (
hydrocarbons,
carbon monoxide, and
nitrogen dioxide) into less-harmful substances (
nitrogen,
carbon dioxide and
water vapor). Palladium is also used in electronics,
dentistry,
medicine, hydrogen purification, chemical applications, and groundwater treatment. Palladium plays a key role in the technology used for
fuel cells, which combine hydrogen and oxygen to produce electricity, heat, and water.
Ore deposits of palladium and other PGMs are rare, and the most extensive deposits have been found in the norite belt of the
Bushveld Igneous Complex covering the
Transvaal Basin in South Africa, the
Stillwater Complex in
Montana, United States, the
Thunder Bay District of
Ontario, Canada, and the
Norilsk Complex in Russia.
Recycling is also a source of palladium, mostly from scrapped catalytic converters. The numerous applications and limited supply sources of palladium result in the metal attracting considerable
investment interest.
Silver Silver is a metallic
chemical element with the
chemical symbol Ag (, from the
Indo-European root *arg- for "grey" or "shining") and
atomic number 47. A soft, white, lustrous
transition metal, it has the highest
electrical conductivity of any element and the highest
thermal conductivity of any metal. The metal occurs naturally in its pure, free form (native silver), as an
alloy with
gold and other metals, and in minerals such as
argentite and
chlorargyrite. Most silver is produced as a byproduct of
copper,
gold,
lead, and
zinc refining. Silver has long been valued as a
precious metal, and it is used to make ornaments,
jewelry, high-value tableware, utensils (hence the term
silverware), and currency
coins. Today, silver metal is also used in electrical contacts and
conductors, in mirrors and in
catalysis of chemical reactions. Its compounds are used in
photographic film, and dilute
silver nitrate solutions and other silver compounds are used as
disinfectants and microbiocides. While many medical
antimicrobial uses of silver have been supplanted by
antibiotics, further research into clinical potential continues.
Cadmium Cadmium is a
chemical element with the symbol
Cd and
atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in
group 12,
zinc and
mercury. Like zinc, it prefers
oxidation state +2 in most of its compounds and like mercury it shows a low melting point compared to
transition metals. Cadmium and its
congeners are not always considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in the Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by
Stromeyer and
Hermann, both in Germany, as an impurity in
zinc carbonate. Cadmium occurs as a minor component in most zinc ores and therefore is a byproduct of zinc production. It was used for a long time as a
pigment and for corrosion resistant plating on
steel while cadmium compounds were used to stabilize
plastic. With the exception of its use in
nickel–cadmium batteries and
cadmium telluride solar panels, the use of cadmium is generally decreasing. These declines have been due to competing technologies, cadmium's
toxicity in certain forms and concentration and resulting regulations. ==p-block elements==