18 - Argon noble gas

Discovered by Lord Rayleigh in 1894

  • Atomic Radius (Å)
  • Cividis
Argon

Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most common gas in the Earth's atmosphere, at 0.934% (9,340 ppmv), making it over twice as abundant as the next most common atmospheric gas, water vapor (which averages about 4000 ppmv, but varies greatly), and 23 times as abundant as the next most common non-condensing atmospheric gas, carbon dioxide (400 ppmv), and more than 500 times as abundant as the next most common noble gas, neon (18 ppmv).

H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
57-71 La-Lu Lanthanides
89-103 Ac-Lr Actinides
 Shell Electrons Orbitals
122 in 1s
282 in 2s + 6 in 2p
382 in 3s + 6 in 3p
ArgonArElectron 1Electron 2Electron 1Electron 2Electron 3Electron 4Electron 5Electron 6Electron 7Electron 8Electron 1Electron 2Electron 3Electron 4Electron 5Electron 6Electron 7Electron 8
colorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field Appearance
39.9  u Atomic Mass
0.71  Å Atomic Radius
87.3  K Boiling Point
18 Group
1.06  Å Covalent Radius
0.00178  g/cm³ Density
−96  kJ/mol Electron Affinity
1s2 2s2 2p6 3s2 3p6 Electron Configuration
[Ne] 3s2 3p6 Electron Configuration (semantic)
18 Electrons
15.8  eV First Ionization Energy
1520.6, 2665.8, 3931, 5771, 7238, 8781, 11995, 13842, 40760, 46186, 52002, 59653, 66199, 72918, 82473, 88576, 397605, 427066  kJ/mol Ionization Energies
84  K Melting Point
3 Mendeleev Number
3 Number of Shells
8 Electron Valency
22 Neutrons
18 Atomic Number
8 Number of Isotopes
3 Period
Gas Phase
18 Protons
2, 8, 8 Electron Shell Occupations