Historical eventJanuary 71939

Marguerite Perey

French physicist Marguerite Perey identified francium, the last element to be discovered in nature rather than by synthesis.

Everything on January 7Original source

In context

When
Saturday, January 7 193987 years ago
Category
Historical eventA dated happening — a battle, treaty, launch, discovery, disaster or decision — recorded on this calendar day.
Era
20th century · 1930s
Recorded from
Wikipedia “On this day” feed

At a glance

Dates: From 1939.

What came beforeAI-assisted

By the 1930s, scientists had identified all elements up to uranium (92) except one gap in the periodic table at atomic number 87. This missing element had been predicted but never isolated or confirmed to exist in nature.

Catalyst / how it startedAI-assisted

Perey was studying the decay products of actinium-227 at the Curie Institute in Paris when she detected an unknown radioactive isotope. She systematically isolated and identified the element, which she named francium after her country.

Who was involvedAI-assisted

Marguerite Perey (1909–1975) was a French nuclear physicist and student of Irène Joliot-Curie. She worked at the Curie Institute, where she conducted the research that led to her discovery.

TimelineAI-assisted

January 7, 1939: Perey identified francium as element 87. She published her findings later that year, confirming the discovery of the last naturally occurring element.

What happened

French physicist Marguerite Perey identified francium, the last element to be discovered in nature rather than by synthesis.

January 7 through the years

Other entries on the same calendar day, in order.

  1. 1939Marguerite Perey
  2. 1994British Aerospace Jetstream 41
  3. 1999Impeachment of Bill Clinton
  4. 2010Nag Hammadi
  5. 2012Hot air balloon
  6. 2015January 2015 Sanaa bombing
  7. 2015Charlie Hebdo shooting
  8. 20202019–20 Puerto Rico earthquakes
  9. 20202019–2020 Spanish government formation
  10. 2023January 2023 Speaker of the United States House of Representatives election
  11. 2025January 2025 Southern California wildfires

Also in 1939

  • September 9World War IIWorld War II: About 3,000 Polish Army troops began a nearly month-long defence of the Hel Peninsula during the German invasion of Poland.
  • September 17World War IISecond World War: The Royal Navy lost its first warship in the war when German submarine U-29 torpedoed and sank HMS Courageous.
  • October 20Pope Pius XIIPope Pius XII (pictured) published his first encyclical, Summi Pontificatus, which critiqued ideologies such as racism, cultural superior…
  • October 14World War IISecond World War: The German submarine U-47 torpedoed and sank the Royal Navy battleship HMS Royal Oak while the latter was anchored at S…
  • December 22All-India Muslim LeagueMembers of the All-India Muslim League observed a "Day of Deliverance" to celebrate the resignations of members of the Indian National Co…
  • May 22Pact of SteelGermany and Italy signed the Pact of Steel, a military and political alliance.
  • November 26Red ArmyThe Soviet Red Army shelled the village of Mainila and then claimed that the fire originated from Finland, giving them a casus belli to l…
  • January 14Queen Maud LandNorway claimed Queen Maud Land, a 2.7-million km2 (1.0-million sq mi) region of Antarctica, as a dependent territory.

Everything we record for 1939 →

Sources

Cite this page

“Marguerite Perey”, What's On This Date, https://whatsonthisdate.com/app/event/marguerite-perey-1939-january-7, accessed October 26, 2026.

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Questions about this entry

When did Marguerite Perey happen?

January 7 1939 — 87 years ago, on a Saturday.

Where does this text come from?

Wikipedia “On this day” feed. Summaries are short adaptations that link back to the source, not reprints. Panels marked AI-assisted were filled where the sources left a heading empty.

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