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).
Read key information and facts about element Argon
|Group in Periodic Table||18|
|Group Name||helium family or neon family|
|Period in Periodic Table||3|
|Block in Periodic Table||p-block|
|Electronic Configuration||[Ne] 3s2 3p6|
|Melting Point||-189.3 °C|
|Boiling Point||-185.8 °C|
|Electronic Shell Structure||[2, 8, 8]|
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 18 to find Argon on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Argon on periodic table look for cross section of group 18 and period 3 in the modern periodic table.
The element Argon was discovered by Lord Rayleigh in year 1894 in United Kingdom . Argon derived its name from the Greek word argos, meaning 'idle'
The table below shows the abundance of Argon in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
|Ppb by weight (1ppb =10^-7 %)|
|Abundance in Universe||0.0002|
|Abundance in Sun||7e-05|
|Abundance in Meteorites||N/A|
|Abundance in Earth's Crust||1.5e-06|
|Abundance in Oceans||4.5e-07|
|Abundance in Humans||N/A|
The solid state structure of Argon is Face Centered Cubic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
and the angles between them Lattice Angles (alpha, beta and gamma).
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
|Space Group Name||Fm_ 3m|
|Space Group Number||225|
|Crystal Structure||Face Centered Cubic|
Argon atoms have 18 electrons and the electronic shell structure is [2, 8, 8] with Atomic Term Symbol (Quantum Numbers) 1S0.
|Number of Electrons (with no charge)||18|
|Number of Protons||18|
|Number of Neutrons||22|
|Shell structure (Electrons per energy level)||[2, 8, 8]|
|Electron Configuration||[Ne] 3s2 3p6|
|Valence Electrons||3s2 3p6|
|Atomic Term Symbol (Quantum Numbers)||1S0|
Shell Structure of Argon - Electrons per energy level
The ground state electronic configuration of Neutral Argon atom is [Ne] 3s2 3p6. The portion of Argon configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Ne]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used.This is important as it is the Valence electrons 3s2 3p6, electrons in the outermost shell that determine the chemical properties of the element.
Complete ground state electronic configuration for the Argon atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6
Argon atomic radius is 71 pm, while it's covalent radius is 97 pm.
71 pm (0.71 Å)
|Atomic Volume||22.3923766816 cm3|
|Covalent Radius||97 pm (0.97 Å)|
|Van der Waals Radius||188 pm|
|Neutron Cross Section||0.65 σa/barns|
The electron affinity of Argon is 0 kJ/mol
Refer to table below for Ionization energies of Argon
|Ionization energy number||Enthalpy - kJ/mol|
Refer to below table for Argon Physical Properties
|Molar Volume||22.3923766816 cm3|
Argon is N/A of electricity. Refer to table below for the Electrical properties of Argon
|Thermal Conductivity||0.01772 W/(m K)|
|Mass Magnetic Susceptibility||-6×10-9|
|Molar Magnetic Susceptibility||-2.4×10-10|
|Volume Magnetic Susceptibility||-1.07×10-8|
|Speed of Sound||319 m/s|
Refer to table below for Thermal properties of Argon
|Melting Point||83.8 K (-189.3 °C)|
|Boiling Point||87.3 K (-185.8 °C)|
|Critical Temperature||150.87 K|
|Heat of Fusion||1.18 kJ/mol|
|Heat of Vaporization||6.5 kJ/mol|
|Heat of Combustion||N/A|
Isotopes of rhodium. Naturally occurring Argon has 3 stable isotope - 36Ar, 38Ar, 40Ar.
|Isotope||Isotope Mass||% Abundance||T half||Decay Mode|
|DOT Hazard Class||2.2|
|NFPA Fire Rating||N/A|
|NFPA Health Rating||N/A|
|NFPA Reactivity Rating||N/A|
List of unique identifiers to search the element in various chemical registry databases
|CAS Number - Chemical Abstracts Service (CAS)||CAS7440-37-1|
|Alkali Metals||Alkaline Earth Metals|
|Transition Metals||Post-Transition Metals|