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Argon

chemical element wi the atomic nummer o 18

Argon is a chemical element wi seembol Ar an atomic nummer 18. It is in group 18 o the periodic table an is a noble gas. Argon is the third maist common gas in the Yird's atmosphere, at 0.93% (9,300 ppm), makin it approximately 23.8 times as abundant as the next maist common atmospheric gas, carbon dioxide (390 ppm), an mair nor 500 times as abundant as the next maist common noble gas, neon (18 ppm). Near aw o this argon is radiogenic argon-40 derived frae the decay o potassium-40 in the Yird's crust. In the universe, argon-36 is bi far the maist common argon isotope, bein the preferred argon isotope produced bi stellar nucleosynthesis in supernovas.

Argon,  18Ar
Vial conteenin a violet glowin gas
General properties
Appearance colourless gas exhibitin a laylock/violet glowe whan placed in a heich voltage electric field
Staundart atomic wecht (Ar, staundart) [39.79239.963] conventional: 39.948
Argon in the periodic cairt
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 Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) 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 Gowd Mercur (element) Thallium Leid (element) 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 Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium
Ne

Ar

Kr
chlorineargonpotassium
Atomic nummer (Z) 18
Group group 18 (noble gases)
Period period 3
Element category   noble gas
Block p-block
Electron confeeguration [Ne] 3s2 3p6
Electrons per shell
2, 8, 8
Pheesical properties
Phase (at STP) gas
Meltin pynt 83.81 K ​(−189.34 °C, ​−308.81 °F)
Bylin pynt 87.302 K ​(−185.848 °C, ​−302.526 °F)
Density (at STP) 1.784 g/L
when liquid (at b.p.) 1.40 g/cm3
Treeple pynt 83.8058 K, ​68.89[1] kPa
Creetical pynt 150.687 K, 4.863[1] MPa
Heat o fusion 1.18 kJ/mol
Heat o vapourisation 6.43 kJ/mol
Molar heat capacity 5R/2 = 20.786 (Cp) J/(mol·K)
Vapour pressur
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K)   47 53 61 71 87
Atomic properties
Oxidation states 0
Electronegativity Pauling scale: no data
Ionisation energies
Covalent radius 106±10 pm
Van der Waals radius 188 pm
Coloyr lines in a spectral range
Spectral lines o Argon
Miscellanea
Creestal structurface-centred cubic (fcc)
Face-centered cubic creestal structur for argon
Speed o soond (gas, 27 °C) 323 m/s
Thermal conductivity 17.72×103  W/(m·K)
Magnetic orderin diamagnetic[2]
CAS Nummer 7440–37–1
History
Diskivery Lord Rayleigh an William Ramsay (1894)
First isolation Lord Rayleigh an William Ramsay (1894)
Main isotopes o argon
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct
36Ar 0.337% - (β+β+) 36S
37Ar syn 35 d ε 37Cl
38Ar 0.063% stable
39Ar trace 269 y β 39K
40Ar 99.600% stable
41Ar syn 109.34 min β 41K
42Ar syn 32.9 y β 42K
Decay modes in parentheses is predict, but hisna yet been observed
| references | in Wikidata

ReferencesEedit

  1. 1.0 1.1 Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nt ed.). CRC Press. p. 4.121. ISBN 1439855110. 
  2. Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.