Argon (Z=18): The Noble Element of the Atmosphere

Essential Role of Argon

Argon (symbol Ar, atomic number 18) is an abundant noble gas in Earth's atmosphere. It constitutes about 0.93% of the Earth's atmosphere by volume. Inert and stable, it plays a crucial role in several industrial and scientific applications.

Contribution of Argon to Industrial Applications

Argon is widely used as a shielding gas in industrial processes, particularly in welding and semiconductor manufacturing. Its low reactivity makes it indispensable for preventing unwanted reactions during these processes.

History of Discovery

1894: First discovery by Lord Rayleigh and William Ramsay
Argon was discovered in 1894 by the British scientist Lord Rayleigh and his colleague William Ramsay, who isolated it from the air. This noble gas was identified due to its inert properties and resistance to any chemical reaction under normal conditions.

1898: Identification of argon as a noble gas
Argon was recognized as a distinct noble gas from other atmospheric elements because it hardly reacts with any other element.

Atomic Structure

Constitution: The argon atom has 18 protons, 22 neutrons, and 18 electrons, with an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶.
Isotopes:

• Argon-40 (¹⁴⁰Ar): stable isotope, representing the majority of natural argon.
• Argon-39 (¹³⁹Ar): radioactive isotope, used in geological and archaeological dating.

Physical Properties

• Monoatomic gas, colorless, odorless, tasteless.
• Molar mass: 39.948 g/mol
• Melting point: -189.34 °C
• Boiling point: -185.85 °C
• Density: ~1.784 g/L (at 0°C and 1 atm)
• Inert at room temperature, does not easily interact with other gases or elements.

Chemical Reactivity

• Noble gas with very low chemical reactivity at room temperature.
• Does not react with other elements at normal temperatures, hence its stability and inertness.
• Forms compounds under extreme conditions (e.g., with fluorine or oxygen, but these reactions require specific conditions).

Industrial and Technological Applications

• Used as a shielding gas in welding and metal cutting (argon welding).
• Shielding gas in the manufacture of semiconductors and flat screens.
• Used in nuclear reactors as a cooling gas.
• Used in medicine for argon lasers in the treatment of certain eye conditions.
• Used as a filling gas in electric light bulbs to extend their lifespan.

Biological and Ecological Role

• Does not play a significant role in biological processes.
• Marginal presence in respiration but not involved in biochemical reactions.

Environmental and Industrial Issues

• Risk of asphyxiation in confined spaces due to its inertness and inability to support human respiration.
• Increased use in industrial applications, but little direct impact on the environment compared to other gases.