Period 6 element

Source: Wikipedia, the free encyclopedia.
Period 6 in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
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A period 6 element is one of the

primordial isotope, 209Bi, has a half-life of more than 1019 years, over a billion times longer than the current age of the universe. As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order; however, there are exceptions, such as gold
.

Properties

This period contains the

radioactive. After bismuth, which has a half-life or more than 1019 years, polonium, astatine, and radon are some of the shortest-lived and rarest elements known; less than a gram of astatine is estimated to exist on earth at any given time.[1]

Atomic characteristics

Chemical element Block Electron configuration
55 Cs Caesium
s-block
 [Xe] 6s1
56 Ba Barium
s-block
 [Xe] 6s2
57 La Lanthanum
f-block [a]
 [Xe] 5d1 6s2 [b]
58 Ce Cerium
f-block
 [Xe] 4f1 5d1 6s2 [b]
59 Pr Praseodymium
f-block
 [Xe] 4f3 6s2
60 Nd Neodymium
f-block
 [Xe] 4f4 6s2
61 Pm Promethium
f-block
 [Xe] 4f5 6s2
62 Sm Samarium
f-block
 [Xe] 4f6 6s2
63 Eu Europium
f-block
 [Xe] 4f7 6s2
64 Gd Gadolinium
f-block
 [Xe] 4f7 5d1 6s2 [b]
65 Tb Terbium
f-block
 [Xe] 4f9 6s2
66 Dy Dysprosium
f-block
 [Xe] 4f10 6s2
67 Ho Holmium
f-block
 [Xe] 4f11 6s2
68 Er Erbium
f-block
 [Xe] 4f12 6s2
69 Tm Thulium
f-block
 [Xe] 4f13 6s2
70 Yb Ytterbium
f-block
 [Xe] 4f14 6s2
71 Lu Lutetium
d-block [a]
 [Xe] 4f14 5d1 6s2
72 Hf Hafnium
d-block
 [Xe] 4f14 5d2 6s2
73 Ta Tantalum
d-block
 [Xe] 4f14 5d3 6s2
74 W Tungsten
d-block
 [Xe] 4f14 5d4 6s2
75 Re Rhenium
d-block
 [Xe] 4f14 5d5 6s2
76 Os Osmium
d-block
 [Xe] 4f14 5d6 6s2
77 Ir Iridium
d-block
 [Xe] 4f14 5d7 6s2
78 Pt Platinum
d-block
 [Xe] 4f14 5d9 6s1 [b]
79 Au Gold
d-block
 [Xe] 4f14 5d10 6s1 [b]
80 Hg Mercury
d-block
 [Xe] 4f14 5d10 6s2
81 Tl Thallium
p-block
 [Xe] 4f14 5d10 6s2 6p1
82 Pb Lead
p-block
 [Xe] 4f14 5d10 6s2 6p2
83 Bi Bismuth
p-block
 [Xe] 4f14 5d10 6s2 6p3
84 Po Polonium
p-block
 [Xe] 4f14 5d10 6s2 6p4
85 At Astatine
p-block
 [Xe] 4f14 5d10 6s2 6p5
86 Rn Radon
p-block
 [Xe] 4f14 5d10 6s2 6p6

s-block elements

Caesium

Main article: Caesium

Caesium or cesium

nuclear reactors
.

Two German chemists, Robert Bunsen and Gustav Kirchhoff, discovered caesium in 1860 by the newly developed method of flame spectroscopy. The first small-scale applications for caesium have been as a "getter" in vacuum tubes and in photoelectric cells. In 1967, a specific frequency from the emission spectrum of caesium-133 was chosen to be used in the definition of the second by the International System of Units. Since then, caesium has been widely used in atomic clocks.

Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids. It has a range of applications in the production of electricity, in electronics, and in chemistry. The radioactive isotope caesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Although the element is only mildly toxic, it is a hazardous material as a metal and its radioisotopes present a high health risk in case of radioactivity releases.

Barium

Main article: Barium

Barium is a

barite), and barium carbonate, BaCO3(witherite). Barium's name originates from Greek
barys (βαρύς), meaning "heavy", describing the high density of some common barium-containing ores.

Barium has few industrial applications, but the metal has been historically used to

superconductors
, and electroceramics.

f-block elements (lanthanides)

Main article:
Lanthanides

The lanthanide or lanthanoid (

rare-earth elements
.

The informal chemical symbol Ln is used in general discussions of lanthanide chemistry. All but one of the lanthanides are

d-block element, is also generally considered to be a lanthanide due to its chemical similarities with the other fourteen. All lanthanide elements form trivalent cations, Ln3+, whose chemistry is largely determined by the ionic radius
, which decreases steadily from lanthanum to lutetium.

Chemical element La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Atomic number 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
Image
Density (g/cm3) 6.162 6.770 6.77 7.01 7.26 7.52 5.244 7.90 8.23 8.540 8.79 9.066 9.32 6.90 9.841
Melting point (°C) 920 795 935 1024 1042 1072 826 1312 1356 1407 1461 1529 1545 824 1652
Atomic electron configuration* 5d1 4f15d1 4f3 4f4 4f5 4f6 4f7 4f75d1 4f9 4f10 4f11 4f12 4f13 4f14 4f145d1
Ln3+ electron configuration*[13] 4f0[14] 4f1 4f2 4f3 4f4 4f5 4f6 4f7 4f8 4f9 4f10 4f11 4f12 4f13

4f14

Ln3+ radius (
pm)[15]
 103 102 99 98.3 97 95.8 94.7 93.8 92.3 91.2 90.1 89 88 86.8 86.1
  • Between initial [Xe] and final 6s2 electronic shells

The lanthanide elements are the group of elements with atomic number increasing from 57 (lanthanum) to 71 (lutetium). They are termed lanthanide because the lighter elements in the series are chemically similar to lanthanum. Strictly speaking, both lanthanum and lutetium have been labeled as group 3 elements, because they both have a single valence electron in the d shell. However, both elements are often included in any general discussion of the chemistry of the lanthanide elements.

In presentations of the

wide-formatted periodic table
inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods).

d-block elements

Lutetium

Main article: Lutetium

Lutetium (

d-block; however, lanthanum
is sometimes placed on the d-block lanthanide position. Chemically, lutetium is a typical lanthanide: its only common oxidation state is +3, seen in its oxide, halides and other compounds. In an aqueous solution, like compounds of other late lanthanides, soluble lutetium compounds form a complex with nine water molecules.

Lutetium was independently discovered in 1907 by French scientist

ytterbia, which was previously thought to consist entirely of ytterbium. The dispute on the priority of the discovery occurred shortly after, with Urbain and von Welsbach accusing each other of publishing results influenced by the published research of the other; the naming honor went to Urbain as he published his results earlier. He chose the name lutecium for the new element but in 1949 the spelling of element 71 was changed to lutetium. In 1909, the priority was finally granted to Urbain and his names were adopted as official ones; however, the name cassiopeium (or later cassiopium) for element 71 proposed by von Welsbach was used by many German scientists until the 1950s. Like other lanthanides, lutetium is one of the elements that traditionally were included in the classification "rare earths
."

Lutetium is rare and expensive; consequently, it has few specific uses. For example, a

catalyst in various chemical reactions. 177Lu-DOTA-TATE is used for radionuclide therapy (see Nuclear medicine
) on neuroendocrine tumours.

Hafnium

Main article: Hafnium

Hafnium is a

stable isotope element to be discovered (rhenium was identified two years later). Hafnium is named for Hafnia, the Latin name for "Copenhagen
", where it was discovered.

Hafnium is used in filaments and electrodes. Some

integrated circuits at 45 nm and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium, titanium, or tungsten
.

Hafnium's large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.

Tantalum

Main article: Tantalum

Tantalum is a

video game systems and computers
. Tantalum, always together with the chemically similar niobium, occurs in the minerals tantalite, columbite and coltan (a mix of columbite and tantalite).

Tungsten

Main article: Tungsten

Tungsten, also known as wolfram, is a chemical element with the chemical symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten directly translatable to heavy stone,[17] though the name is volfram in Swedish to distinguish it from Scheelite, in Swedish alternatively named tungsten.

A hard, rare

brittle[19] and hard, making it difficult to work. However, very pure tungsten, though still hard, is more ductile, and can be cut with a hard-steel hacksaw.[20]

The unalloyed elemental form is used mainly in electrical applications. Tungsten's many alloys have numerous applications, most notably in incandescent

catalysts
.

Tungsten is the only metal from the third transition series that is known to occur in biomolecules, where it is used in a few species of bacteria. It is the heaviest element known to be used by any living organism. Tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life.[21][22]

Rhenium

Main article: Rhenium

Rhenium is a

third-highest melting point and highest boiling point of any element. Rhenium resembles manganese chemically and is obtained as a by-product of molybdenum and copper ore's extraction and refinement. Rhenium shows in its compounds a wide variety of oxidation states
ranging from −1 to +7.

Discovered in 1925, rhenium was the last

stable element to be discovered. It was named after the river Rhine
in Europe.

superalloys of rhenium are used in the combustion chambers, turbine blades, and exhaust nozzles of jet engines, these alloys contain up to 6% rhenium, making jet engine construction the largest single use for the element, with the chemical industry's catalytic uses being next-most important. Because of the low availability relative to demand, rhenium is among the most expensive of metals, with an average price of approximately US$4,575 per kilogram (US$142.30 per troy ounce) as of August 2011; it is also of critical strategic military importance, for its use in high performance military jet and rocket engines.[23]

Osmium

Main article: Osmium

Osmium is a

platinum family and is the densest naturally occurring element, with a density of 22.59 g/cm3 (slightly greater than that of iridium and twice that of lead). It is found in nature as an alloy, mostly in platinum ores; its alloys with platinum, iridium, and other platinum group metals are employed in fountain pen tips, electrical contacts, and other applications where extreme durability and hardness are needed.[24]

Iridium

Main article: Iridium

Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element (after osmium) and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.

Iridium was discovered in 1803 among insoluble impurities in natural

stable isotopes
; the latter is the more abundant of the two.

The most important iridium compounds in use are the salts and acids it forms with

organometallic compounds used in industrial catalysis, and in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, as in high-end spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators
.

Iridium is found in meteorites with an abundance much higher than its average abundance in the Earth's crust. For this reason the unusually high abundance of iridium in the clay layer at the Cretaceous–Paleogene boundary gave rise to the Alvarez hypothesis that the impact of a massive extraterrestrial object caused the extinction of dinosaurs and many other species 66 million years ago. It is thought that the total amount of iridium in the planet Earth is much higher than that observed in crustal rocks, but as with other platinum group metals, the high density and tendency of iridium to bond with iron caused most iridium to descend below the crust when the planet was young and still molten.

Platinum

Main article: Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78.

Its name is derived from the Spanish term platina, which is literally translated into "little silver".

malleable, ductile, precious, gray-white transition metal
.

Platinum has six naturally occurring isotopes. It is one of the rarest elements in the Earth's crust and has an average abundance of approximately 5 μg/kg. It is the least reactive metal. It occurs in some nickel and copper ores along with some native deposits, mostly in South Africa, which accounts for 80% of the world production.

As a member of the

pre-Columbian South American natives to produce artifacts. It was referenced in European writings as early as 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian
origin in 1748 that it became investigated by scientists.

Platinum is used in

platinum-resistance thermometers, dentistry equipment, and jewelry. Because only a few hundred tonnes are produced annually, it is a scarce material, and is highly valuable. Being a heavy metal, it leads to health issues upon exposure to its salts, but due to its corrosion resistance, it is not as toxic as some metals.[27] Its compounds, most notably cisplatin, are applied in chemotherapy against certain types of cancer.[28]

Gold

Main article: Gold

Gold is a dense, soft, shiny, malleable and ductile metal. It is a chemical element with the symbol Au and atomic number 79.

Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a

alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with tellurium
.

Gold resists attacks by individual acids, but it can be dissolved by the

acid test
.

Gold has been a valuable and highly sought-after

gold certificate and gold coin currencies were issued in the U.S. in 1932. In Europe, most countries left the gold standard with the start of World War I
in 1914 and, with huge war debts, failed to return to gold as a medium of exchange.

A total of 165,000

troy ounces or, in terms of volume, about 8500 m3, or a cube 20.4 m on a side. The world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry.[30]

Besides its widespread monetary and symbolic functions, gold has many practical uses in

electric wiring, colored-glass production and even gold leaf
eating.

It has been claimed that most of the Earth's gold lies at its core, the metal's high density having made it sink there in the planet's youth. Virtually all of the gold that mankind has discovered is considered to have been deposited later by

meteorites which contained the element. This supposedly explains why, in prehistory, gold appeared as nuggets on the earth's surface.[31][32][33][34][35]

Mercury

Main article: Mercury (element)

Mercury is a

freezing point of −38.83 °C and boiling point of 356.73 °C, mercury has one of the narrowest ranges of its liquid state of any metal.[36][37][38]

Mercury occurs in deposits throughout the world mostly as

mercuric chloride or methylmercury
), inhalation of mercury vapor, or eating seafood contaminated with mercury.

Mercury is used in

fluoresce
, making visible light.

p-block elements

Thallium

Main article: Thallium

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray

other metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy. Both discovered the new element in residues of sulfuric acid
production.

Approximately 60–70% of thallium production is used in the

rat poisons and insecticides. Its use has been reduced or eliminated in many countries because of its nonselective toxicity. Because of its use for murder, thallium has gained the nicknames "The Poisoner's Poison" and "Inheritance Powder" (alongside arsenic).[40]

Lead

Main article: Lead

Lead is a main-group

heavy metals
. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.

Lead is used in building construction,

atomic nuclei
.

Lead, at certain exposure levels, is a poisonous substance to animals as well as for human beings. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.

Bismuth

Main article: Bismuth

Bismuth is a

other metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery white color when newly made, but often seen in air with a pink tinge owing to the surface oxide. Bismuth metal has been known from ancient times, although until the 18th century it was often confused with lead and tin, which each have some of bismuth's bulk physical properties. The etymology is uncertain but possibly comes from Arabic bi ismid meaning having the properties of antimony[41] or German words weisse masse or wismuth meaning "white mass".[42]

Bismuth is the most naturally

thermal conductivity
.

Bismuth has classically been considered to be the heaviest naturally occurring stable element, in terms of atomic mass. Recently, however, it has been found to be very slightly radioactive: its only primordial isotope

billion times the estimated age of the universe.[43]

Bismuth compounds (accounting for about half the production of bismuth) are used in cosmetics, pigments, and a few pharmaceuticals. Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead has become more apparent in recent years, alloy uses for bismuth metal (presently about a third of bismuth production), as a replacement for lead, have become an increasing part of bismuth's commercial importance.

Polonium

Main article: Polonium

Polonium is a

radioactive element, polonium is chemically similar to bismuth[44] and tellurium, and it occurs in uraniumores. Polonium has been studied for possible use in heating spacecraft. As it is unstable, all isotopes of polonium are radioactive. There is disagreement as to whether polonium is a post-transition metal or metalloid.[45][46]

Astatine

Main article: Astatine

Astatine is a

radioactive chemical element with the symbol At and atomic number 85. It occurs on the Earth only as the result of decay of heavier elements, and decays away rapidly, so much less is known about this element than its upper neighbors in the periodic table. Earlier studies have shown this element follows periodic trends, being the heaviest known halogen, with melting and boiling points
being higher than those of lighter halogens.

Until recently most of the chemical characteristics of astatine were inferred from comparison with other elements; however, important studies have already been done. The main difference between astatine and

nonmetals result in positive oxidation states, with +1 best portrayed by monohalides and their derivatives, while the higher are characterized by bond to oxygen and carbon. Attempts to synthesize astatine fluoride have been met with failure. The second longest-living astatine-211 is the only one to find a commercial use, being useful as an alpha emitter
in medicine; however, only extremely small quantities are used, and in larger ones it is very hazardous, as it is intensely radioactive.

Astatine was first produced by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè in the University of California, Berkeley in 1940. Three years later, it was found in nature; however, with an estimated amount of less than 28 grams (1 oz) at given time, astatine is the least abundant element in Earth's crust among non-transuranium elements. Among astatine isotopes, four (with mass numbers 215, 217, 218 and 219) are present in nature as the result of decay of heavier elements; however, the most stable astatine-210 and the industrially used astatine-211 are not.

Radon

Main article: Radon

Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless[47] noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Radon is one of the densest substances that remains a gas under normal conditions. It is also the only gas that is radioactive under normal conditions, and is considered a health hazard due to its radioactivity. Intense radioactivity also hindered chemical studies of radon and only a few compounds are known.

Radon is formed as part of the normal radioactive decay chain of uranium and thorium. Uranium and thorium have been around since the earth was formed and their most common isotope has a very long half-life (14.05 billion years). Uranium and thorium, radium, and thus radon, will continue to occur for millions of years at about the same concentrations as they do now.[48] As the radioactive gas of radon decays, it produces new radioactive elements called radon daughters or decay products. Radon daughters are solids and stick to surfaces such as dust particles in the air. If contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.[49]

Radon is responsible for the majority of the public exposure to

spring waters and hot springs.[50]

Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA estimates.[51]

Biological role

Of the period 6 elements, only tungsten and the early lanthanides[52] are known to have any biological role in organisms, and even then only in lower organisms (not mammals). However, gold, platinum, mercury, and some lanthanides such as gadolinium have applications as drugs.

Toxicity

Most of the period 6 elements are toxic (for instance lead) and produce heavy-element poisoning. Promethium, polonium, astatine and radon are radioactive, and therefore present radioactive hazards.

Notes

  1. ^ Caesium is the spelling recommended by the International Union of Pure and Applied Chemistry (IUPAC).[6] The American Chemical Society (ACS) has used the spelling cesium since 1921,[7][8] following Webster's New International Dictionary. The element was named after the Latin word caesius, meaning "bluish gray". More spelling explanation at ae/oe vs e.
  2. ^ Along with rubidium (39 °C [102 °F]), francium (estimated at 27 °C [81 °F]), mercury (−39 °C [−38 °F]), and gallium (30 °C [86 °F]); bromine is also liquid at room temperature (melting at −7.2 °C, 19 °F) but it is a halogen, not a metal.[9]

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