The Elements  

In General > s.a. atomic physics.
* Origin: Nucleosynthetic processes in the course of the evolution of the Universe and the galaxies contained within include primordial nucleosynthesis, stellar evolution, and explosive nucleosynthesis in single and binary systems.
* Superheavy elements: The search is fascinating, and offers sensitive tests of theories of nuclear physics and chemistry (for example by observing their decays), but experiments typically last several months, and at the end produce few, of the order of two or three, superheavy nuclei.
* Naming: Names must end in "-ium," "-ine," or "-on" depending on the grouping of elements they belong to.
@ General references: Ball 04; Rauscher & Patkós in(11)-a1011, Woosley et al PT(19)feb [origin].
@ Periodic system: Babaev & Hefferlin in(96); Scerri AS(97) [and electrons], SA(98)sep [evolution]; Kak Sandhan(04)phy [history, Mendeleev]; Kibler FC(07)qp/06 [application of SO(4,2) × SU(2)]; Scerri AS(08)jan [history and developments in classification system]; Kragh a1207/EPJH [early scientific interest in the very heavy elements]; Lagerkvist 12 [and Mendeleev]; news sn(19)jan, pt(19)mar [history].
@ New elements: news cnn(16)jun [113, 115, 117, 118 named]; Kragh a1708 [the search for superheavy elements].
@ Related topics: Oganessian & Rykaczewski PT(15)aug [island of stability]; He & Garoufalidis a1811 [end of the periodic table, highest possible atomic number]; news sn(19)mar [lifetimes of unstable elements].
> Online resources: American Elements website [properties and uses of elements]; The Periodic Table of Videos website.

0: Positronium, Ps
* Idea: An e+e bound state; Orthopositronium (spins pointing in the same direction) has a lifetime of about 150 ns.
* Use: Measuring the annihilation decay rates provides unique tests of QED.
@ References: Vallery et al PRL(03) + pw(03)may [lifetime]; Fleischer et al PRL(06) + pn(06)jan [Ps−]; Kiessling a1807 [and electron-positron annihilation]; Gurung et al PRL(20) [spectroscopy, discrepancy with QED].

1: Hydrogen, H

2: Helium, He > s.a. early-universe nucleosynthesis; quantum systems; superfluids; types of superconductors.
* Idea: The second most abundant element in the universe, but it was only seen in the Sun's spectrum in 1868, and discovered on Earth (in a uranium mineral) in 1895!
* Isotopes: 8He has been observed, and seems to have a "halo" of 4 neutrons surrounding a 4He core; 2001, 9He with an extra neutron in a second outer shell was formed for 10−20 seconds by shooting 11Be nuclei into a target of 9Be atoms.
* Physical properties: It is the only substance that won't freeze at absolute zero temperature, at least at at atmospheric pressure.
* Properties of solid He-4: At 1 atm, it remains a gas until cooled to 4.2 K, where it liquefies; Upon further cooling in equilibrium with its vapor, at about 2.2 K the liquid undergoes a spectacular phase transition to a superfluid state; And due to quantum mechanical zero-point motion, it remains a liquid upon cooling to as close to absolute zero as physicists have been able to reach; It solidifies only with the application of some 25 atm of pressure at very low temperature.
* Supersolid claim: A confusing, at times frustrating story of claims and disproofs about the properties of solid 4He; > s.a. solid matter.
@ General references: Hallock PT(98)jun [3He in 2D]; Chen et al PLB(01) [9He isotope]; news pw(06)oct [universal abundance puzzle]; news pn(08)may [2He observed!]; Lindgren a0810 [fine-structure controversy]; Modarres & Moshfegh PhyA(09) [thermodynamics of normal liquid 3He]; Rieger Phy(12)jun [why doesn't helium solidify at low temperatures?]; > s.a. matter [anti-alpha particles].
@ Related topics: news pt(10)jun [DOE begins rationing 3He]; news pw(12)jul [He molecules in extreme magnetic fields?]; Gasparini Phy(12) [evidence for a liquid phase in 2D 3He]; McMahon et al RMP(12) [properties under extreme conditions]; Tariq et al PRL(13) + Friedrich Phy(13) [fragile LiHe van der Waals molecule]; news wired(15)jul [the trouble with helium availability]; Atiyah MPLA(17)-a1703 [models of the stable isotopes 4He and 3He]; news pt(20)jun [on He availability].

3: Lithium, Li > s.a. early-universe nucleosynthesis and standard cosmological model [7Li problem]; matter near black holes [lithium synthesis].
* Formation: Of all the elements of the periodic table, lithium has perhaps the most complicated and mysterious origins; It's the only element that can be produced in large quantities in three ways: in Big Bang nucleosynthesis during the first three minutes, in nuclear reactions initiated by cosmic rays in the interstellar medium, and in stars (evolved low-mass stars, novae, and supernova explosions), when 3He and 4He fuse into 7Be, which undergoes beta decay within tens of days to form 7Li.
@ References: news ab(12)jul [lithium abundance and galactic evolution]; Tajitsu et al Nat(15)mar [evidence for frmation in stars].

4: Beryllium, Be

5: Boron, B
* Properties: It forms several complex structures that are hard to tell apart; It reacts with nearly everything, and even a trace of impurities can drastically change the structure and properties of the boron crystal.
@ References: Eremets et al Sci(01) + pw(01)jul [superconductivity at high pressure]; news ns(09)sep [hardness]; news ns(12)jun [boron atoms can form triple bonds and link up in chains].

6: Carbon, C

7: Nitrogen, N
* New forms: 2001, Non-molecular polymer-like opaque solid with semiconducting properties, formed around 140 GPa, hysteresis effect makes it stable at atmospheric p, can store energy.
@ References: Eremets et al Nat(01)may + pw(01)may [new form]; Pilyugin et al A&A(03)ap/02, Chiappini et al A&A(05)ap [origin]; Vangioni et al a1710 [in the interstellar medium].

8: Oxygen, O > s.a. phase transitions [in solid oxygen].
@ References: Shimizu et al Nat(98)jun [superconducting]; Gorelli et al PRL(99) [O4 molecules at high p]; Freiman & Jodl PRP(04) [solid O].

9: Fluorine, F
@ References: news sci(15)sep [neutrinos created most of the fluorine in the universe].

10: Neon, Ne

11: Sodium, Na

12: Magnesium, Mg

13: Aluminum, Al

14: Silicon, Si
* History: 2001, Japanese scientists formed Si cage clusters, analogous to C fullerenes [@ Hiura et al PRL(01) + pn(01)feb].
* Use: A vital material for the semiconductor industry and one of the most studied elements in all of science.
@ References: news pw(10)aug [melts when cooled]; news sn(11)mar, ns(12)apr, pw(12)jun [silicene as the new graphene?]; Taylor PT(16)dec [extreme forms]; news pt(18)feb [thermal conductivity, ultrapure silicon and isotopic purity].

15: Phosphorus, P

16: Sulfur, S

17: Chlorine, Cl

18: Argon, Ar

19: Potassium, K

20: Calcium, Ca

21: Scandium, Sc

22: Titanium, Ti

23: Vanadium, V

24: Chromium, Cr

25: Manganese, Mn

26: Iron, Fe
@ References: Kuwayama et al PRL(20) [equation of state of liquid Fe under extreme conditions].

27: Cobalt, Co

28: Nickel, Ni

29: Copper, Cu

30: Zinc, Zn > s.a. neutron stars.

31: Gallium, Ga

32: Germanium, Ge

33: Arsenic, As
* Properties: Metalloid.

34: Selenium, Se
* Properties: Non-metal.

35: Bromine, Br
* Properties: Halogen liquid.

36: Krypton, Kr
* Properties: Noble gas.

37: Rubidium, Rb
* Properties: Alkaline metal.

38: Strontium, Sr
* Properties: Alkaline earth metal.

39: Yttrium, Y
* History: Its discoverer, Johann Gadolin, named it after the Swedish town of Ytterby.
* Properties: Transition metal; in pure form, silvery-colored, but found in most rare-earth mineral combinations.
* Use: Make red phosphors for TV and computer monitors.

40: Zirconium, Zr
* Properties: Transition metal.
@ References: news sn(19)jan [Zr-88 captures neutrons with extreme efficiency].

41: Niobium, Nb
* Comments: Named after Niobe, daughter of Tantalus; Used in searches for fractional charges.

42: Molybdenum, Mo
* Comments: From the greek "molybdos", lead; Occurs only in impure forms in nature.

43: Technetium, Tc
* History: The first element to be synthetically produced, in 1937.
* Where: The only one of the first 92 elements not found naturally on Earth (except possibly in minute traces).
* Properties: Radioactive, but 99Tc has τ1/2 = 210,000 yr.
* Use: Used in nuclear medicine for examination of liver and blood, and to identify some stars.

44: Ruthenium, Ru

45: Rhodium, Rh

46: Palladium, Pd

47: Silver, Ag
* Properties: Transition metal.

48: Cadmium, Cd
* Properties: Transition metal.

49: Indium, In
* Properties: Metal.

50: Tin, Sn
@ References: news ea(12)jun [tin-100 is "doubly magic"].

51: Antimony, Sb

52: Tellurium, Te

53: Iodine, I

54: Xenon, Xe
* Where: A noble gas, present in our atmosphere with concentrations below one part per million.
* Use: For commercial production, xenon is extracted by liquefying air at low temperature and high pressure, and then separating the xenon from other components. Its main use is in various types of lights, including some automobile headlamps, stroboscopes, and as an exciter in some laser applications.
* Radioactive isotope: Xe-124 has a half-life at about 18 sextillion years, the longest ever directly measured in a radioactive substance and about 1 trillion times longer than the age of the universe.
* Puzzle: Our atmosphere contains far less xenon, relative to the lighter noble gases, than meteorites similar to the rocky material that formed the Earth.
@ References: news SA(12)oct [the mysterious case of the missing xenon]; news sn(19)apr [rare two-neutrino double electron capture decay of xenon-124 seen].

55: Cesium, Cs

56: Barium, Ba

57: Lanthanum, La

58: Cerium, Ce

59: Praseodymium, Pr

60: Neodymium, Nd

61: Promethium, Pm

62: Samarium, Sm

63: Europium, Eu

64: Gadolinium, Gd

65: Terbium, Tb

66: Dysprosium, Dy

67: Holmium, Ho

68: Erbium, Er

69: Thulium, Tm

70: Ytterbium, Yb > s.a. bose-einstein condensation.
* Properties: Has the longest-lived known excited state, 3700 days [@ Roberts et al PRL(97)].

71: Lutetium, Lu

72: Hafnium, Hf

73: Tantalum, Ta
* Properties: Ta-180 is the rarest naturally occurring isotope.

74: Tungsten, W

75: Rhenium, Re

76: Osmium, Os
* Properties: Each atom has eight "valence" electrons available for covalent bonding, the highest number known.

77: Iridium, Ir
> Online resources: Wikipedia page.

78: Platinum, Pt

79: Gold, Au
@ References: news CfA(13)jul [Earth's gold came from colliding neutron stars]; news sn(17)jan [measured and calculated ionization energies now agree].

80: Mercury, Hg

81: Thallium, Tl

82: Lead, Pb
@ References: Krygier et al PRL(19) + news sn(19)nov [lead becomes stronger than steel under extreme pressures].

83: Bismuth, Bi

84: Polonium, Po
* Properties: The only element with a simple cubic crystal structure (the result of the complicated set of orbital energy states of the electrons and their spin-orbit couplings, made more complicated by the interplay of relativistic effects–specifically the relativistic increase in electron mass at high velocities); Because of its crystal structure, its elastic anisotropy is greater than for any other solid; It has 36 isotopes, more than any other element, and is highly radioactive; Polonium is a hazardous element that appears in the air and soil and in such plants as tobacco, tea, and mushrooms.
@ References: news pn(07)jun.

85: Astatine, At
* Properties: It is the rarest element on Earth (in 1953, Isaac Asimov estimated that the worldwide total of astatine in nature was 0.07 grams); It is radioactive, with a half-life of just 8.1 hours.
@ References: news SA(13)may [ionization potential measured at CERN].

86: Radon, Rn

87: Francium, Fr
* Properties: Least stable of first 103 elements, less than 1 oz exists on Earth at any time, but not hard to produce.
@ Trapped: news pn(96)may; PT(96)jun; Simsarian et al PRL(96).

88: Radium, Ra

89: Actinium, Ac

90: Thorium, Th

91: Protactinium, Pa

92: Uranium, U
@ References: Bernstein a0906 [isotope separation with gas centrifuges].

93: Neptunium, Np

94: Plutonium, Pu
* Properties: One of the most unusual metals – it's not magnetic and it does not conduct electricity well; The material also changes its size dramatically with even the slightest changes in its temperature and pressure; Used as fuel for nuclear weapons and power plants.
@ References: news pn(07)mar [theory of properties].

95: Americium, Am

96: Curium, Cm

97: Berkelium, Bk

98: Californium, Cf

99: Einsteinium, Es

100: Fermium, Fm
> Online resources: see Wikipedia page on the Transfermium Wars.

101: Mendelevium, Md

102: Nobelium, No
@ References: news sn(18)jun [shape and structure of the nucleus].

103: Lawrencium, Lr

104: Rutherfordium, Rf
@ References: Wiedenhöver Phy(12)jul [details of the superheavy nucleus' 256Rf nonspherical shape and internal structure from gamma-ray spectroscopy].

105: Dubnium, Db (Americans had proposed calling it hahnium)

106: Seaborgium, Sg
@ References: Schädel et al Nat(97)jul [chemical properties].

107: Bohrium, Bh
* Properties: Extremely unstable, and not found in nature; Experiments on chemical properties done with longer-lived (about 20 sec) isotope at LBL.

108: Hassium, Hs

109: Meitnerium, Mt

110: Darmstadtium, Ds
* History: 1994, Discovered at the GSI lab in Darmstadt, and quickly seen in other experiments at Berkeley and the JINR laboratory in Russia – However, none of the observations confirmed the others because they all produced different isotopes of the new element; 2003, Confirmed [@ Ginter et al PRC(03) + pw(03)jul].

111: Roentgenium, Rg
* History: 2003, Discovered at the GSI lab in Darmstadt [news pw(03)oct].

112: Copernicium, Cn
* History: 1996, Discovered at the GSI lab in Darmstadt, in an experiment in which physicists smashed zinc atoms into a lead target; This resulted in the production of a single atom of the new element, with an atomic mass of 277.
* Properties: τ = 280 ms.
@ References: news pn(96)feb [discovery]; Armbruster & Hessberger SA(98)sep [2 atoms of 112 made].

113: Nihonium, Nh (ex "Ununtrium", Uut)
* History: Announced in 2004 by Dubna group as decay product from #115; Atoms lived up to 1.2 s; 2012, Not yet officially accepted.
@ References: Oganessian et al PRC(04) + pw(04)feb; news nat(12)sep; news sn(16)nov [name official].

114: Flerovium, Fl (ex "Ununquadium", Uuq)
* History: 1999, Russian-Livermore discovery, unconfirmed; 2009, Results confirmed by the LBNL team.
* Properties: τ = 30 s; Island of stability?
@ References: news pw(99)jan, PT(99)apr [reported discovery]; Oganessian et al SA(00)jan [island of stability]; Stavsetra PRL(09), news pt(09)sep, ns(10)jun, nyt(11)jun [confirmation].
> Online resources: see Wikipedia page.

115: Moscovium, Mc (ex "Ununpentium", Uup)
* History: 2004, Dubna group announcement of the production of 4 atoms, that lived for about 90 ms; 2011, Discovery not yet officially accepted, but report that the third atom has been created in Japan; 2013, Discovery confirmed.
@ References: Oganessian et al PRC(04) + pw(04)feb; Rudolph et al PRL(13) + news PhysOrg(13)aug [discovery confirmed]; news sn(16)nov [name official].

116: Livermorium, Lv (ex "Ununhexium", Uuh)
* History: 1999, Discovered at Lawrence Berkeley National Lab, by crashing krypton atoms into Pb atoms [@ news pn(99)jun, pn(06)oct, nyt(11)jun].
> Online resources: see Wikipedia page.

117: Tennessine, Ts (ex "Ununseptium", Uus)
* History: 2010, Discovery announced as product of fusion reactions by a collaboration of Russian and US physicists; 2014, Discovery confirmed.
@ References: Oganessian et al PRL(10) + Hofmann Phy(10)apr [discovery]; Miller PT(10)jun [decay gives nine more previously unobserved nuclei]; Oganessian et al PRL(12) + Greiner Phy(12); Scerri SA(13)jun [the periodic table has no gaps, for the first time]; news Phy(14)may [confirmation]; news sn(16)nov [name official].

118: Oganesson, Og (ex "Ununoctium", Uuo)
* History: 1999, Discovery announced at Lawrence Berkeley National Lab, like #116 [@ news pn(99)jun, pw(99)jun]; 2001–2002, Discovery retracted after an internal review committee found that data purporting to show the existence of the new element had been fabricated [@ news pn(01)aug, pw(01)aug]; 2006, Discovery announced again by JINR-Lawrence Livermore National Lab collaboration [@ news pn(06)oct, pw(06)oct].
@ References: Oganessian et al PRL(12) + Greiner Phy(12); Jerabek et al PRL(18) + viewpoint + news sn(16)nov [name official]; news pw(18)feb [properties].

119: ?

120: ?
@ References: Smolanczuk PLB(01).

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