Chlorine Potassium

Argon (Ar)

From Wikipedia, the free encyclopediaArgon 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).

Argon in the periodic table

Symbol

Atomic number

Group

Period

Block

Element category

Noble Gas

Physical properties

Phase at STP

Gas

Density

1.784 g/cm³

Atomic weight

39.9481 u

Melting point

83.81 K
-189.34 °C
-308.812 °F

Boiling point

87.302 K
-185.848 °C
-302.5264 °F

Atomic properties

Electronegativity (Pauling Scale)

Electron affinity

-96 kJ/mol

Oxidation states

Ionization energies

1	1520.6 kJ/mol
2	2665.8 kJ/mol
3	3931 kJ/mol
4	5771 kJ/mol
5	7238 kJ/mol
6	8781 kJ/mol
7	11995 kJ/mol
8	13842 kJ/mol
9	40760 kJ/mol
10	46186 kJ/mol
11	52002 kJ/mol
12	59653 kJ/mol
13	66199 kJ/mol
14	72918 kJ/mol
15	82473 kJ/mol
16	88576 kJ/mol
17	397605 kJ/mol
18	427066 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)

[Ne] 3s² 3p⁶

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶

Electrons per shell

2, 8, 8

History

Discovered

1894

Discovered by

Lord Rayleigh
William Ramsay