Francium and Aluminum: The Rare France-Named Metal and the Aluminum Naming Saga

Episode snapshot

This Chemistry World episode dives into francium, the named after France alkali metal with atomic number 87 and an Earthly abundance of less than a kilogram at any moment. It traces its discovery by Marguerite Perey in 1939, explains its fleeting 21 minute half life and the decay chain that leads from actinium to francium, and reveals how the element earned its name after Perey rejected catium as a possible label. The program also recounts the aluminum naming history, from Davy's aluminum to the IUPAC suffix standardization, and notes how American pronunciation diverged from the British tradition. It closes with a teaser about the next element on Chemistry In Its Element.

• Francium’s origin in the decay chains of actinium and its rarity on Earth
• Naming history and the moment francium was accepted as the official name
• Aluminum naming controversy and suffix standardization
• Real vs expected reactivity in the heaviest alkali metals

Francium and its place in the periodic table

The podcast builds its narrative around the element named after France, francium, which sits at atomic number 87 in the alkali metal family. It emphasizes how little francium is present on Earth, with estimates suggesting less than a kilogram at any given time, due to its very short half life and continuous decay in radioactive processes. The discussion highlights the historical context of the periodic table’s gaps, noting that when Mendeleev first published his table, gaps existed for undiscovered elements. Henry Moseley later linked elements to their atomic numbers, clarifying that francium would occupy the position beneath cesium in the table, the last of a group of highly reactive alkali metals.

The episode then recounts Perey’s discovery. In 1929 Madame Curie hired a young Marguerite Catherine Perey as lab staff, and a decade later she identified francium in a salt, using careful purification to observe emissions from actinium decay products. Perey’s careful purification allowed her to monitor the specific emissions that trace francium formation, revealing that most actinium slowly decays via beta emission to thorium, while a small fraction alpha-decays to francium. Francium’s own fleeting existence—half-life about 21 minutes—means it rapidly beta-decays back toward lighter elements, complicating detection and characterization. The narrative also recounts the naming decision, with Perey proposing catium initially, which was met with limited enthusiasm, and ultimately the element being named francium after her homeland.

The decay chain that reveals francium’s origin

The podcast outlines two simple decay rules: for each alpha emission, the product’s atomic number decreases by 2; for each beta emission, the product’s atomic number increases by 1. Starting from actinium 89, the chain usually proceeds via beta decay to thorium 90, then alpha decay to radium 88, with a small 1 percent branch that forms francium 87 directly from actinium. Francium itself quickly beta-decays to radium, but its 21-minute half-life makes direct observation difficult. Perey’s work focused on isolating an actinium salt and isolating emissions from actinium to observe the short-lived francium signal in decay sequences.

Reactivity and misperceptions

In a twist that challenges intuition, francium is not the most reactive metal as predicted by trends in the periodic table. The outer electrons in the heaviest alkali metals are influenced by strong nuclear charge, which can offset the expected ease of ionization. Measurements have shown that removing an electron from francium requires about 393 kilojoules per mole, somewhat higher than cesium, indicating cesium remains the practically most readily ionized alkali metal. The podcast uses this to illustrate the nuance in atomic physics where relativistic effects play a role in electron behavior near heavy nuclei.

Aluminum naming and nomenclature

The episode also revisits the naming of element number 13, aluminum. Humphry Davy used the name aluminum based on a root from alum, but the International Union of Pure and Applied Chemistry later standardized the suffix to em, which is how the word is commonly rendered in many regions today. A historical note explains that Americans adopted the original spelling aluminum in 1925, and in practice this led to differing pronunciations: Americans often say aluminum, while many English speakers continue to say aluminium. The narrative highlights how standardization can shape pronunciation and spelling across cultures.

Conclusion and preview

The podcast ends by pointing listeners to the next element story in Chemistry In Its Element, noted for its impact on lightweight materials and appetite for everyday items such as beverage cans, foreshadowing the aluminum-focused episode to come. The host signs off, inviting curiosity about the chemistry that shapes our world.