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Ar Argon
Element Information, Facts, Properties, Trends, Uses, Comparison with other elements

18
Ar
Argon
Element 18 of Periodic table is Argon with atomic number 18, atomic weight 39.948. Argon, symbol Ar, has a Face Centered Cubic structure and Colorless color. Argon is a Noble Gas element. It is part of group 18 (helium family or neon family). Know everything about Argon Facts, Physical Properties, Chemical Properties, Electronic configuration, Atomic and Crystal Structure.
18 Ar - Argon | SchoolMyKids

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).

It belongs to group 18 of the periodic table having trivial name noble gases, aerogens.

Argon Facts

Read key information and facts about element Argon

NameArgon
Atomic Number18
Atomic SymbolAr
Atomic Weight39.948
PhaseGas (Monoatomic Gas )
ColorColorless
Appearancecolorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field
ClassificationNoble Gas
Group in Periodic Table18
Group Namehelium family or neon family
Period in Periodic Tableperiod 3
Block in Periodic Tablep -block
Electronic Configuration[Ne] 3s2 3p6
Electronic Shell Structure (Electrons per shell)2, 8, 8
Melting Point83.8 K
Boiling Point87.3 K
CAS NumberCAS7440-37-1
Neighborhood Elements
123456789101112131415161718
1
1
H
Hydrogen
1.008

Atomic #

Electronic Shell #

Symbol
Name
Atomic Weight
HGas
HgLiquid
CSolid
Metals
Metalloids
NonMetals
Alkali metals
Alkali earth metals
Lanthanoids
Transition metals
Post-transition metals
Other nonmetals
Halogens
Nobel gas
Actinoids
2
He
Helium
4.003
2
3
Li
Lithium
6.941
4
Be
Beryllium
9.012
5
B
Boron
10.811
6
C
Carbon
12.011
7
N
Nitrogen
14.007
8
O
Oxygen
15.999
9
F
Fluorine
18.998
10
Ne
Neon
20.180
3
11
Na
Sodium
22.990
12
Mg
Magnesium
24.305
13
Al
Aluminium
26.982
14
Si
Silicon
28.085
15
P
Phosphorus
30.974
16
S
Sulfur
32.065
17
Cl
Chlorine
35.453
18
Ar
Argon
39.948
4
19
K
Potassium
39.098
20
Ca
Calcium
40.078
21
Sc
Scandium
44.956
22
Ti
Titanium
47.867
23
V
Vanadium
50.941
24
Cr
Chromium
51.996
25
Mn
Manganese
54.938
26
Fe
Iron
55.845
27
Co
Cobalt
58.933
28
Ni
Nickel
58.693
29
Cu
Copper
63.546
30
Zn
Zinc
65.409
31
Ga
Gallium
69.723
32
Ge
Germanium
72.640
33
As
Arsenic
74.922
34
Se
Selenium
78.960
35
Br
Bromine
79.904
36
Kr
Krypton
83.798
5
37
Rb
Rubidium
85.468
38
Sr
Strontium
87.620
39
Y
Yttrium
88.906
40
Zr
Zirconium
91.224
41
Nb
Niobium
92.906
42
Mo
Molybdenum
95.940
43
Tc
Technetium
98
44
Ru
Ruthenium
101.070
45
Rh
Rhodium
102.906
46
Pd
Palladium
106.420
47
Ag
Silver
107.868
48
Cd
Cadmium
112.411
49
In
Indium
114.818
50
Sn
Tin
118.710
51
Sb
Antimony
121.760
52
Te
Tellurium
127.600
53
I
Iodine
126.904
54
Xe
Xenon
131.293
6
55
Cs
Cesium
132.905
56
Ba
Barium
137.327
57 - 71
La - Lu
Lanthanides
72
Hf
Hafnium
178.490
73
Ta
Tantalum
180.948
74
W
Tungsten
183.840
75
Re
Rhenium
186.207
76
Os
Osmium
190.230
77
Ir
Iridium
192.217
78
Pt
Platinum
195.078
79
Au
Gold
196.967
80
Hg
Mercury
200.590
81
Tl
Thallium
204.383
82
Pb
Lead
207.200
83
Bi
Bismuth
208.980
84
Po
Polonium
209
85
At
Astatine
210
86
Rn
Radon
222
7
87
Fr
Francium
223
88
Ra
Radium
226
89 - 103
Ac - Lr
Actinides
104
Rf
Rutherfordium
261
105
Db
Dubnium
262
106
Sg
Seaborgium
266
107
Bh
Bohrium
264
108
Hs
Hassium
277
109
Mt
Meitnerium
268
110
Ds
Darmstadtium
281
111
Rg
Roentgenium
272
112
Cn
Copernicium
285
113
Nh
Nihonium
284
114
Fl
Flerovium
289
115
Mc
Moscovium
288
116
Lv
Livermorium
292
117
Ts
Tennessine
294
118
Og
Oganesson
294
Lanthanides
57
La
Lanthanum
138.905
58
Ce
Cerium
140.116
59
Pr
Praseodymium
140.908
60
Nd
Neodymium
144.240
61
Pm
Promethium
145
62
Sm
Samarium
150.360
63
Eu
Europium
151.964
64
Gd
Gadolinium
157.250
65
Tb
Terbium
158.925
66
Dy
Dysprosium
162.500
67
Ho
Holmium
164.930
68
Er
Erbium
167.259
69
Tm
Thulium
168.934
70
Yb
Ytterbium
173.040
71
Lu
Lutetium
174.967
Actinides
89
Ac
Actinium
227
90
Th
Thorium
232.038
91
Pa
Protactinium
231.036
92
U
Uranium
238.029
93
Np
Neptunium
237
94
Pu
Plutonium
244
95
Am
Americium
243
96
Cm
Curium
247
97
Bk
Berkelium
247
98
Cf
Californium
251
99
Es
Einsteinium
252
100
Fm
Fermium
257
101
Md
Mendelevium
258
102
No
Nobelium
259
103
Lr
Lawrencium
262

How to Locate Argon on Periodic Table

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.

Argon History

The element Argon was discovered by Lord Rayleigh and W. Ramsay in year 1894 in United Kingdom. Argon was first isolated by Lord Rayleigh and W. Ramsay in 1894. Argon derived its name from the Greek word argos, meaning 'idle'.

They discovered the gas by comparing the molecular weights of nitrogen prepared by liquefaction from air and nitrogen prepared by chemical means. It is the first noble gas to be isolated.

Argon Presence: Abundance in Nature and Around Us

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 %)ppb by atoms (1ppb =10^-7 %)
Abundance in Universe2000006000
Abundance in Sun700002000
Abundance in Meteorites--
Abundance in Earth's Crust1500780
Abundance in Oceans45070
Abundance in Humans--

Crystal Structure of Argon

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.

Unit Cell Parameters

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)

abc
525.6 pm525.6 pm525.6 pm

and the angles between them Lattice Angles (alpha, beta and gamma).

alphabetagamma
π/2 π/2 π/2

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 NameFm_ 3m 18 Ar Argon - Crystal Structure | SchoolMyKids
Oxidation StatesSpace Group Number225
Crystal StructureFace Centered Cubic

Argon Atomic and Orbital Properties

Argon atoms have 18 electrons and the electronic shell structure is [2, 8, 8] with Atomic Term Symbol (Quantum Numbers) 1S0.

Atomic Number18
Number of Electrons (with no charge)18
Number of Protons18
Mass Number40
Number of Neutrons22
Shell structure (Electrons per energy level)2, 8, 8
Electron Configuration[Ne] 3s2 3p6
Valence Electrons3s2 3p6
Valence (Valency)0
Main Oxidation States0
Oxidation States0
Atomic Term Symbol (Quantum Numbers)1S0

Bohr Atomic Model of Argon - Electrons per energy level

18 Ar Argon - Electron Shell Structure | SchoolMyKids
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Ground State Electronic Configuration of Argon - neutral Argon atom

Abbreviated electronic configuration of Argon

The ground state abbreviated 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.

Unabbreviated electronic configuration of neutral Argon

Complete ground state electronic configuration for the Argon atom, Unabbreviated electronic configuration

1s2 2s2 2p6 3s2 3p6

Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.

  • As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
  • The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
  • Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.
  • Electron configuration of Argon
    Atomic Structure of Argon

    Argon atomic radius is 71 pm, while it's covalent radius is 97 pm.

    Atomic Radius Calculated

    71 pm (0.71 Å)

    Atomic Radius Empirical

    71 pm (0.71 Å)

    Atomic Volume22.4134 cm3/mol
    Covalent Radius97 pm (0.97 Å)
    Van der Waals Radius188 pm
    Neutron Cross Section0.65
    Neutron Mass Absorption 0.0006

    Atomic Spectrum of Argon

    Atomic Spectrum of Argon | SchoolMyKids

    Argon Chemical Properties: Argon Ionization Energies and electron affinity

    The electron affinity of Argon is 0 kJ/mol.

    Valence0
    Electronegativity-
    ElectronAffinity0 kJ/mol

    Ionization Energy of Argon

    Refer to table below for Ionization energies of Argon

    Ionization energy numberEnthalpy - kJ/mol
    1st1520.6
    2nd2665.8
    3rd3931
    4th5771
    5th7238
    6th8781
    7th11995
    8th13842
    9th40760
    10th46186
    11th52002
    12th59653
    13th66199
    14th72918
    15th82473
    16th88576
    17th397605
    18th427066

    Argon Physical Properties

    Refer to below table for Argon Physical Properties

    Density0.001784 g/cm3
    Molar Volume22.4134 cm3/mol

    Elastic Properties

    Young Modulus-
    Shear Modulus-
    Bulk Modulus -
    Poisson Ratio-

    Hardness of Argon - Tests to Measure of Hardness of Element

    Mohs Hardness-
    Vickers Hardness-
    Brinell Hardness-

    Argon Electrical Properties

    Argon is Conductor of electricity. Refer to table below for the Electrical properties ofArgon

    Electrical Conductivity-
    Resistivity-
    Superconducting Point-

    Argon Heat and Conduction Properties

    Thermal Conductivity0.01772 W/(m K)
    Thermal Expansion-

    Argon Magnetic Properties

    Magnetic TypeDiamagnetic
    Curie Point-
    Mass Magnetic Susceptibility-6e-9 m3/kg
    Molar Magnetic Susceptibility-2.4e-10 m3/mol
    Volume Magnetic Susceptibility-1.07e-8

    Optical Properties of Argon

    Refractive Index1.000281

    Acoustic Properties of Argon

    Speed of Sound319 m/s

    Argon Thermal Properties - Enthalpies and thermodynamics

    Refer to table below for Thermal properties of Argon

    Melting Point83.8 K (-189.35°C, -308.8299999999999 °F)
    Boiling Point87.3 K (-185.85°C, -302.5299999999999 °F)
    Critical Temperature150.87 K
    Superconducting Point-

    Enthalpies of Argon

    Heat of Fusion1.18 kJ/mol
    Heat of Vaporization6.5 kJ/mol
    Heat of Combustion-

    Argon Isotopes - Nuclear Properties of Argon

    Argon has 24 isotopes, with between 30 and 53 nucleons. Argon has 3 stable naturally occuring isotopes.

    Isotopes of Argon - Naturally occurring stable Isotopes: 36Ar, 38Ar, 40Ar.

    IsotopeZNIsotope Mass% AbundanceT halfDecay Mode
    30Ar181230Synthetic
    31Ar181331Synthetic
    32Ar181432Synthetic
    33Ar181533Synthetic
    34Ar181634Synthetic
    35Ar181735Synthetic
    36Ar1818360.3365%StableN/A
    37Ar181937Synthetic
    38Ar1820380.0632%StableN/A
    39Ar182139Synthetic
    40Ar18224099.6003%Stable
    41Ar182341Synthetic
    42Ar182442Synthetic
    43Ar182543Synthetic
    44Ar182644Synthetic
    45Ar182745Synthetic
    46Ar182846Synthetic
    47Ar182947Synthetic
    48Ar183048Synthetic
    49Ar183149Synthetic
    50Ar183250Synthetic
    51Ar183351Synthetic
    52Ar183452Synthetic
    53Ar183553Synthetic

    Regulatory and Health - Health and Safety Parameters and Guidelines

    Database Search

    List of unique identifiers to search the element in various chemical registry databases

    DatabaseIdentifier number
    CAS Number - Chemical Abstracts Service (CAS)CAS7440-37-1
    RTECS NumberRTECSCF2300000
    CID Number CID23968
    Gmelin Number-
    NSC Number-