- 🇬🇧 Argon
- 🇺🇦 Аргон
- 🇨🇳 氬
- 🇳🇱 Argon
- 🇫🇷 Argon
- 🇩🇪 Argon
- 🇮🇱 ארגון
- 🇮🇹 Argo
- 🇯🇵 アルゴン
- 🇵🇹 Argão
- 🇪🇸 Argón
- 🇸🇪 Argon
- 🇷🇺 Аргон
- Name: argon
- Symbol: Ar
- Atomic number: 18
- Relative atomic mass (Ar): 39.948 (1) g, r [see notes g r]
- Standard state: gas at 298 K
- Appearance: colourless
- Classification: Non-metallic
- Group in periodic table: 18
- Group name: Noble gas
- Period in periodic table: 3
- Block in periodic table: p
- Shell structure: 2.8.8
- CAS Registry: 7440-37-1
Argon atoms have 18 electrons and the shell structure is 2.8.8. The ground state electronic configuration of neutral argon is [Ne].3s2.3p6 and the term symbol of argon is 1S0.
Argon: description
Argon is a colourless and odourless gas present to a very small extent in the atmosphere. Argon is very inert (indeed it is referred to as one of the noble gases) and is not known to form true chemical compounds. It makes a good atmosphere for working with air-sensitive materials since it is heavier than air and less reactive than N2. Today, the chemical symbol for argon is Ar but until 1957 its sybol was simply A.
argon
Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.
Argon: physical properties
- Density of the chemical elements on a miniature periodic table spark table Density of solid: 1616 kg m-3
- Molar volume of the chemical elements on a miniature periodic table spark table Molar volume: 22.56 cm3
- Thermal conductivity of the chemical elements on a miniature periodic table spark table Thermal conductivity: 0.01772 W m‑1 K‑1
Argon: heat properties
- Melting point on a miniature periodic table spark table Melting point: 83.8 [‑189.3 °C (‑308.7 °F)] K
- Boiling point on a miniature periodic table spark table Boiling point: 87.3 [‑185.8 °C (‑302.4 °F)] K
- Enthalpy of fusion on a miniature periodic table spark table Enthalpy of fusion: 20.5 kJ mol-1
Argon: atom sizes
- Atomic radius (empirical) of the chemical elements on a miniature periodic table spark table Atomic radius (empirical): (no data) pm
- Covalent (single bond) radius on a periodic table spark table Molecular single bond covalent radius: 96 (coordination number 1,2) ppm
- van der Waals radius on a periodic table spark table van der Waals radius: 183 ppm
Argon: electronegativities
- Pauling electronegativity of the chemical elements on a miniature periodic table spark table Pauling electronegativity: (no data) (Pauling units)
- Allred-Rochow electronegativity of the chemical elements on a miniature periodic table spark tableAllred Rochow electronegativity: 3.20 (Pauling units)
- Mulliken-Jaffe electronegativity of the chemical elements on a miniature periodic table spark tableMulliken-Jaffe electronegativity: 3.19 (12.5% s orbital)
Argon: orbital properties
- First ionization energy the chemical elements on a miniature periodic table spark table First ionisation energy: 1520.57 kJ mol‑1
- Second ionization energy the chemical elements on a miniature periodic table spark table Second ionisation energy: 2665.86 kJ mol‑1
- Third ionization energy the chemical elements on a miniature periodic table spark table Third ionisation energy: 3930 kJ mol‑1
Argon: abundances
- Chemical elements abundance by weight in the universe on a miniature periodic table spark tableUniverse: 200000 ppb by weight
- Chemical elements abundance by weight in the earth's crust on a miniature periodic table spark tableCrustal rocks: 1500 ppb by weight
- Chemical elements abundance by weight in humans on a miniature periodic table spark tableHuman: (no data) ppb by weight
Argon: crystal structure
Argon: biological data
- Human abundance by weight of the chemical elements on a miniature periodic table spark table Human abundance by weight: (no data) ppb by weight
Argon has no biological role.
Argon: uses
Argon: reactions
Reactions of argon as the element with air, water, halogens, acids, and bases where known.
Argon: binary compounds
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of argon where known.
Argon: compound properties
Bond strengths; lattice energies of argon halides, hydrides, oxides (where known); and reduction potentials where known.
Argon: history
Argon was discovered by Sir William Ramsay, Lord Rayleigh in 1894 at UCL, London, England. Origin of name: from the Greek word "argos" meaning "inactive".Argon: isotopes
Argon isotopes are used as precursors in the production of radioisotopes. Ar-40 and Ar-38 are used in the production of radioactive K-38 which can be used as a blood flow tracer. Ar-40 is used in the production of radioactive Ar-41 which is used to trace gas flows.
Argon: isolation
Isolation: argon is present to a small extent in the atmosphere and is obtained as a byproduct from the liquefaction and separation of air. This would not normally be carried out in the laboratory and argon is available commercially in cylinders at high pressure.