text: ytterbium ytterbium is a chemical element with symbol yb and atomic number 70 . it is the fourteenth and penultimate element in the lanthanide series , which is the basis of the relative stability of its + 2 oxidation state . however , like the other lanthanides , its most common oxidation state is + 3 , seen in its oxide , halides and other compounds . in aqueous solution , like compounds of other late lanthanides , soluble ytterbium compounds form complexes with nine water molecules . because of its closed - shell electron configuration , its density and melting and boiling points differ from those of the other lanthanides . in 1878 , the swiss chemist jean charles galissard de marignac separated in the rare earth " erbia " another independent component , which he called " ytterbia " , for ytterby , the village in sweden near where he found the new component of erbium . he suspected that ytterbia was a compound of a new element that he called " ytterbium " ( in total , four elements were named after the village , the others being yttrium , terbium and erbium ) . in 1907 , the new earth " lutecia " was separated from ytterbia , from which the element " lutecium " ( now lutetium ) was extracted by georges urbain , carl auer von welsbach , and charles james . after some discussion , marignac 's name " ytterbium " was retained . a relatively pure sample of the metal was obtained only in 1953 . at present , ytterbium is mainly used as a dopant of stainless steel or active laser media , and less often as a gamma ray source . natural ytterbium is a mixture of seven stable isotopes , which altogether are present at concentrations of 3 parts per million . this element is mined in china , the united states , brazil , and india in form of the minerals monazite , euxenite , and xenotime . the ytterbium concentration is low , because the element is found among many other rare earth elements ; moreover , it is among the least abundant ones . once extracted and prepared , ytterbium is somewhat hazardous as an eye and skin irritant . the metal is a fire and explosion hazard . characteristics physical properties ytterbium is a soft , malleable and ductile chemical element that displays a bright silvery luster when in its pure form . it is a rare earth element , and it is readily attacked and dissolved by the strong mineral acids . it reacts slowly with cold water and it oxidizes slowly in air . ytterbium has three allotropes labeled by the greek letters alpha , beta and gamma ; their transformation temperatures are − 13 ° c and 795 ° c , although the exact transformation temperature depends on the pressure and stress . the beta allotrope exists at room temperature , and it has a face - centered cubic crystal structure . the high - temperature gamma allotrope has a body - centered cubic crystalline structure . the alpha allotrope has a hexagonal crystalline structure and is stable at low temperatures . normally , the beta allotrope has a metallic electrical conductivity , but it becomes a semiconductor when exposed to a pressure of about 16 , 000 atmospheres ( 1 . 6 gpa ) . its electrical resistivity increases ten times upon compression to 39 , 000 atmospheres ( 3 . 9 gpa ) , but then drops to about 10 % of its room - temperature resistivity at about 40 , 000 atm ( 4 . 0 gpa ) . in contrast with the other rare - earth metals , which usually have antiferromagnetic and / or ferromagnetic properties at low temperatures , ytterbium is paramagnetic at temperatures above 1 . 0 kelvin . however , the alpha allotrope is diamagnetic . with a melting point of 824 ° c and a boiling point of 1196 ° c , ytterbium has the smallest liquid range of all the metals . contrary to most other lanthanides , which have a close - packed hexagonal lattice , ytterbium crystallizes in the face - centered cubic structure . as a result , its density ( 6 . 973 g / cm3 ) is significantly lower than , e.g. , those of the neighboring elements thulium ( 9 . 32 g / cm3 ) and lutetium ( 9 . 841 g / cm3 ) . the melting and boiling points of ytterbium are also significantly lower than those of thulium and lutetium . these properties stem from the closed - shell electron configuration of ytterbium ( [ xe ] ) , which causes only the two 6s electrons to be available for metallic bonding ( in contrast to the other lanthanides where three electrons are available ) . chemical properties ytterbium metal tarnishes slowly in air . finely dispersed ytterbium readily oxidizes in air and under oxygen . mixtures of powdered ytterbium with or burn with a luminous emerald - green flame . ytterbium reacts with hydrogen to form various non - stoichiometric hydrides . ytterbium dissolves slowly in water , but quickly in acids , liberating hydrogen gas . ytterbium is quite electropositive , and it reacts slowly with cold water and quite quickly with hot water to form ytterbium ( iii ) hydroxide : 2 yb ( s ) + 6 h2o ( l ) → 2 yb ( oh ) 3 ( aq ) + 3 h2 ( g ) ytterbium reacts with all the halogens : 2 yb ( s ) + 3 f2 ( g ) → 2 ( s ) [ white ] 2 yb ( s ) + 3 cl2 ( g ) → 2 ( s ) [ white ] 2 yb ( s ) + 3 br2 ( g ) → 2 ( s ) [ white ] 2 yb ( s ) + 3 i2 ( g ) → 2 ( s ) [ white ] the ytterbium ( iii ) ion absorbs light in the near infrared range of wavelengths , but not in visible light , so the mineral ytterbia , , is white in color and the salts of ytterbium are also colorless . ytterbium dissolves readily in dilute sulfuric acid to form solutions that contain the colorless yb ( iii ) ions , which exist as complexes : 2 yb ( s ) + 3 h2so4 ( aq ) → 2 [ yb ( h2o ) 9 ] 3 + ( aq ) + 3 so2 − 4 ( aq ) + 3 h2 ( g ) yb ( ii ) vs. yb ( iii ) although usually trivalent , ytterbium readily forms divalent compounds . this behavior is unusual to most lanthanides , which almost exclusively form compounds with an oxidation state of + 3 . the + 2 state has a valence electron configuration of because the fully filled f - shell gives more stability . the yellow - green ytterbium ( ii ) ion is a very strong reducing agent and decomposes water , releasing hydrogen gas , and thus only the colorless ytterbium ( iii ) ion occurs in aqueous solution . samarium and thulium also behave this way in the + 2 state , but europium ( ii ) is stable in aqueous solution . ytterbium metal behaves similarly to europium metal and the alkaline earth metals , dissolving in ammonia to form blue electride salts . isotopes natural ytterbium is composed of seven stable isotopes : , , , , , 174yb , and , with 174yb being the most abundant isotope , at 31 . 8 % of the natural abundance ) . 27 radioisotopes have been observed , with the most stable ones being 169yb with a half - life of 32 . 0 days , with a half - life of 4 . 18 days , and with a half - life of 56 . 7 hours . all of its remaining radioactive isotopes have half - lives that are less than two hours and most of these have half - lives are less than 20 minutes . ytterbium also has 12 meta states , with the most stable being ( t1 / 2 46 seconds ) . the isotopes of ytterbium range in atomic weight from 147 . atomic mass unit ( u ) for to 180 . u for . the primary decay mode of ytterbium isotopes lighter than the most abundant stable isotope , 174yb , is electron capture , and the primary decay mode for those heavier than 174yb is beta decay . the primary decay products of ytterbium isotopes lighter than 174yb are thulium isotopes , and the primary decay products of ytterbium isotopes with heavier than 174yb are lutetium isotopes . occurrence ytterbium is found with other rare earth elements in several rare minerals . it is most often recovered commercially from monazite sand ( 0 . 03 % ytterbium ) . the element is also found in euxenite and xenotime . the main mining areas are china , the united states , brazil , india , sri lanka , and australia ; and reserves of ytterbium are estimated as one million tonnes . ytterbium is normally difficult to separate from other rare earths , but ion - exchange and solvent extraction techniques developed in the mid- to late 20th century have simplified separation . known compounds of ytterbium are rare and have not yet been well characterized . the abundance of ytterbium in the earth 's crust is about 3 mg / kg . as an even - numbered lanthanide , in accordance with the oddo - harkins rule , ytterbium is significantly more abundant than its immediate neighbors , thulium and lutetium , which occur in the same concentrate at levels of about 0 . 5 % each . the world production of ytterbium is only about 50 tonnes per year , reflecting the fact that ytterbium has few commercial applications . microscopic traces of ytterbium are used as a dopant in the yb : yag laser , a solid - state laser in which ytterbium is the element that undergoes stimulated emission of electromagnetic radiation . production it is somewhat difficult to separate ytterbium from other lanthanides due to its similar properties . as a result , the process is somewhat long . first , minerals such as monazite or xenotime are dissolved into various acids , such as sulfuric acid . ytterbium can then be separated from other lanthanides by ion exchange , as can other lanthanides . the solution is then applied to a resin , which different lanthanides bond to in different matters . this is then dissolved using complexing agents , and due to the different types of bonding exhibited by the different lanthanides , it is possible to isolate the compounds . ytterbium is separated from other rare earths either by ion exchange or by reduction with sodium amalgam . in the latter method , a buffered acidic solution of trivalent rare earths is treated with molten sodium - mercury alloy , which reduces and dissolves + . the alloy is treated with hydrochloric acid . the metal is extracted from the solution as oxalate and converted to oxide by heating . the oxide is reduced to metal by heating with lanthanum , aluminium , cerium or zirconium in high vacuum . the metal is purified by sublimation and collected over a condensed plate . compounds the chemical behavior of ytterbium is similar to that of the rest of the lanthanides . most ytterbium compounds are found in the + 3 oxidation state and its salts in this oxidation state are nearly colorless . like europium , samarium , and thulium , the trihalides of ytterbium can be reduced to the dihalides by hydrogen , zinc dust , or by the addition of metallic ytterbium . the + 2 oxidation state only occurs in solid compounds and reacts in some ways similarly to the alkaline earth metal compounds ; for example , ytterbium ( ii ) oxide ( ) shows the same structure as calcium oxide ( cao ) . halides ytterbium forms both dihalides and trihalides with the halogens fluorine , chlorine , bromine , and iodine . the dihalides are susceptible to oxidation to the trihalides at room temperature and disproportionate to the trihalides and metallic ytterbium at high temperature : 3 → 2 + yb ( x f , cl , br , i ) some ytterbium halides are used as reagents in organic synthesis . for example , ytterbium ( iii ) chloride ( ) is a lewis acid and can be used as a catalyst in the and diels – alder reactions . ytterbium ( ii ) iodide ( ) may be used , like samarium ( ii ) iodide , as a reducing agent for coupling reactions . ytterbium ( iii ) fluoride ( ) is used as an inert and non - toxic tooth filling as it continuously releases fluoride ions , which are good for dental health , and is also a good x - ray contrast agent . oxides ytterbium reacts with oxygen to form ytterbium ( iii ) oxide ( ) , which crystallizes in the " rare - earth c - type sesquioxide " structure which is related to the fluorite structure with one quarter of the anions removed , leading to ytterbium atoms in two different six coordinate ( non - octahedral ) environments . ytterbium ( iii ) oxide can be reduced to ytterbium ( ii ) oxide ( ) with elemental ytterbium , which crystallizes in the same structure as sodium chloride . history ytterbium was discovered by the swiss chemist jean charles galissard de marignac in the year 1878 . while examining samples of gadolinite , marignac found a new component in the earth then known as erbia , and he named it ytterbia , for ytterby , the swedish village near where he found the new component of erbium . marignac suspected that ytterbia was a compound of a new element that he called " ytterbium " . in 1907 , the french chemist georges urbain separated marignac 's ytterbia into two components : and lutecia . would later become known as the element ytterbium , and lutecia would later be known as the element lutetium . the austrian chemist carl auer von welsbach independently isolated these elements from ytterbia at about the same time , but he called them aldebaranium and cassiopeium ; the american chemist charles james also independently isolated these elements at about the same time . urbain and welsbach accused each other of publishing results based on the other party . the commission on atomic mass , consisting of frank wigglesworth clarke , wilhelm ostwald , and georges urbain , which was then responsible for the attribution of new element names , settled the dispute in 1909 by granting priority to urbain and adopting his names as official ones , based on the fact that the separation of lutetium from marignac 's ytterbium was first described by urbain ; after urbain 's names were recognized , neoytterbium was reverted to ytterbium . the chemical and physical properties of ytterbium could not be determined with any precision until 1953 , when the first nearly pure ytterbium metal was produced by using ion - exchange processes . the price of ytterbium was relatively stable between 1953 and 1998 at about us $ 1 , 000 / kg . applications source of gamma rays the 169yb isotope ( with a half - life of 32 days ) , which is created along with the short - lived isotope ( half - life 4 . 2 days ) by neutron activation during the irradiation of ytterbium in nuclear reactors , has been used as a radiation source in portable x - ray machines . like x - rays , the gamma rays emitted by the source pass through soft tissues of the body , but are blocked by bones and other dense materials . thus , small 169yb samples ( which emit gamma rays ) act like tiny x - ray machines useful for radiography of small objects . experiments show that radiographs taken with a 169yb source are roughly equivalent to those taken with x - rays having energies between 250 and 350 kev . 169yb is also used in nuclear medicine . world 's most stable atomic clock ytterbium clocks hold the record for stability with ticks stable to within less than two parts in 1 quintillion ( 2 × 10 − 18 ) . the clocks developed at the national institute of standards and technology ( nist ) rely on about 10 , 000 rare - earth atoms cooled to 10 ( 10 millionths of a degree above absolute zero ) and trapped in an optical lattice — a series of pancake - shaped wells made of laser light . another laser that " ticks " 518 trillion times per second provokes a transition between two energy levels in the atoms . the large number of atoms is key to the clocks ' high stability . doping of stainless steel ytterbium can also be used as a dopant to help improve the grain refinement , strength , and other mechanical properties of stainless steel . some ytterbium alloys have rarely been used in dentistry . ytterbium as dopant of active media the ytterbium + 3 ion is used as a doping material in active laser media , specifically in solid state lasers and double clad fiber lasers . ytterbium lasers are highly efficient , have long lifetimes and can generate short pulses ; ytterbium can also easily be incorporated into the material used to make the laser . ytterbium lasers commonly radiate in the 1 . 06 – 1 . 12 µm band being optically pumped at wavelength 900 nm – 1 µm , dependently on the host and application . the small quantum defect makes ytterbium a prospective dopant for efficient lasers and power scaling . the kinetic of excitations in ytterbium - doped materials is simple and can be described within the concept of effective cross - sections ; for most ytterbium - doped laser materials ( as for many other optically pumped gain media ) , the relation holds , although the application to the ytterbium - doped composite materials was under discussion . usually , low concentrations of ytterbium are used . at high concentrations , the ytterbium - doped materials show ( glass fibers ) or even a switch to broadband emission ( crystals and ceramics ) instead of efficient laser action . this effect may be related with not only overheating , but also with conditions of charge compensation at high concentrations of ytterbium ions . much progress has been made in the power scaling lasers and amplifiers produced with ytterbium ( yb ) doped optical fibers . power levels have increased from the 1 kw regimes due to the advancements in components as well as the yb doped fibers themselves . fabrication of low na , large mode area ( lma ) fibers enable achievement of near perfect beam qualities ( m2 performance . all of which contribute to increased power levels in 1 µm systems . others ytterbium metal increases its electrical resistivity when subjected to high stresses . this property is used in stress gauges to monitor ground deformations from earthquakes and explosions . visible light waves oscillate faster than microwaves , and therefore optical clocks can be more precise than caesium atomic clocks . the physikalisch - technische ( ) is working on several such optical clocks . the model with one single ytterbium ion caught in an ion trap is highly accurate . the optical clock based on it is exact to 17 digits after the decimal point . a pair of experimental atomic clocks based on ytterbium atoms at the national institute of standards and technology ( nist ) has set a new record for stability . nist physicists report in the august 22 , 2013 issue of science express that the ytterbium clocks ' ticks are stable to within less than two parts in 1 quintillion ( 1 followed by 18 zeros ) , roughly 10 times better than the previous best published results for other atomic clocks . the clocks would be accurate within a second for a period comparable to the age of the universe . currently , ytterbium is being investigated as a possible replacement for magnesium in high density pyrotechnic payloads for kinematic infrared decoy flares . as ytterbium ( iii ) oxide has a significantly higher emissivity in the infrared range than magnesium oxide , a higher radiant intensity is obtained with ytterbium - based payloads in comparison to those commonly based on magnesium / teflon / viton ( mtv ) . precautions although ytterbium is fairly stable chemically , it is stored in airtight containers and in an inert atmosphere such as a nitrogen - filled dry box to protect the metal from air and moisture . all compounds of ytterbium are treated as highly toxic , although initial studies appear to indicate that the danger is minimal . ytterbium compounds are , however , known to cause irritation to the human skin and eyes , and some might be teratogenic . metallic ytterbium dust can spontaneously combust , and the resulting fumes are hazardous . ytterbium fires cannot be extinguished using water , and only dry chemical class d fire extinguishers can extinguish the fires .