On August 13, 1894, English physicist John William Strutt (Lord Rayleigh) (1842–1919) and Scottish chemist Sir William Ramsay (1852–1916) announced the discovery of a new chemical element: Argon ($\text{Ar}$, $Z=18$).

In March 1895, Ramsay isolated terrestrial Helium ($\text{He}$, $Z=2$) from the uranium mineral cleveite, discovering an entire new column in the Periodic Table: the Noble Gases (Group 18).

The Atmospheric Nitrogen Anomaly & Argon Discovery

Lord Rayleigh noticed a persistent discrepancy in gas densities: nitrogen extracted from atmospheric air was always $0.5\%$ heavier than chemically synthesized nitrogen gas.

Ramsay’s Isolation Procedure

Ramsay passed atmospheric air over red-hot magnesium to remove oxygen and nitrogen ($\text{Mg}_3\text{N}_2$), leaving an unreactive dense gas residue ($1.78\,\text{g/L}$):

$$\text{Atmospheric Air} \xrightarrow{\text{Hot Mg}} \text{Argon } (\text{Ar}, \text{atomic mass } 39.95)$$

They named it Argon (from Greek argos, meaning “inactive/lazy”) because it formed no chemical compounds.

Terrestrial Isolation of Helium (1895)

In March 1895, Ramsay treated cleveite ore with sulfuric acid, liberating a light gas whose spectrum matched Pierre Janssen and Norman Lockyer’s 1868 solar $D_3$ line ($587.49\,\text{nm}$)—isolating Helium on Earth for the first time.

Nobel Prizes in Physics & Chemistry (1904)

  • Lord Rayleigh: Awarded the 1904 Nobel Prize in Physics.
  • William Ramsay: Awarded the 1904 Nobel Prize in Chemistry.

In quantum mechanics, Noble Gases represent completely filled, ultra-stable quantum electron shells ($\text{ns}^2 \text{np}^6$).

Key Takeaways

  • Year: 1894
  • Key Figures: Lord Rayleigh & William Ramsay
  • Core Discoveries: Discovered Argon (1894) and isolated terrestrial Helium (1895), founding Group 18 Noble Gases.
  • Double Nobel Laureates: Awarded the 1904 Nobel Prizes in Physics and Chemistry.
  • Quantum Relevance: Discovered closed-shell inert quantum electronic configurations ($\text{ns}^2 \text{np}^6$).