On June 26, 1886, 33-year-old French chemist Ferdinand Frédéric Henri Moissan (1852–1907) presented his triumph to the French Academy of Sciences (Comptes Rendus, Vol. 102).
Moissan accomplished one of the most dangerous and elusive goals in 19th-century chemistry: isolating elemental Fluorine gas ($\text{F}_2$).
Low-Temperature Electrolysis Apparatus¶
Because fluorine is the most chemically reactive and electronegative element in the Periodic Table ($X = 3.98$), previous attempts to isolate it resulted in violent explosions or destruction of equipment.
Moissan’s Platinum Cell¶
Moissan constructed a specialized platinum U-tube cooled to $-50^\circ\text{C}$ containing a solution of potassium hydrogen difluoride ($\text{KHF}_2$) dissolved in anhydrous liquid hydrogen fluoride ($\text{HF}$):
- Corrosion Resistance: Used inert platinum-iridium electrodes and fluorspar ($\text{CaF}_2$) stoppers.
- Electrolytic Reaction: Applying a high-voltage current evolved pale yellow-green Fluorine gas ($\text{F}_2$) at the anode:
$$2\text{HF}_{(l)} \xrightarrow{\text{electrolysis, }-50^\circ\text{C}} \text{H}_{2\,(g)} + \text{F}_{2\,(g)}$$
Nobel Prize in Chemistry (1906)¶
Moissan was awarded the 1906 Nobel Prize in Chemistry for his isolation of fluorine and invention of the electric arc furnace.
In quantum mechanics, fluorine’s extreme electronegativity and reactivity arise from its compact valence shell configuration ($1\text{s}^2 2\text{s}^2 2\text{p}^5$), exhibiting a maximum electron affinity ($\text{EA} = 3.40\,\text{eV}$).
Key Takeaways¶
- Year: 1886
- Key Figure: Henri Moissan (French Chemist)
- Core Discovery: Isolated Elemental Fluorine ($\text{F}_2$) via low-temperature platinum cell electrolysis.
- Nobel Laureate: Awarded the 1906 Nobel Prize in Chemistry.
- Quantum Relevance: Demonstrates maximum quantum electronegativity and electron affinity in halogen shell filling ($2\text{p}^5$).