Inventions & Discoveries · Science and discovery

Radioactivity

1896 · 19th century · Also known as Radioactive decay, Nuclear decay

Radioactivity, or radioactive decay, is the process by which an unstable atomic nucleus loses energy by radiation, discovered in 1896 by Henri Becquerel when uranium salts blackened a photographic plate wrapped in black paper. Marie Curie showed that the rays were a property of atoms; with Pierre Curie she coined the term "radioactivity" and isolated polonium and radium. Ernest Rutherford and Frederick Soddy were the first to realise that many decay processes turn one element into another. Decay is used to estimate the ages of rocks and organic matter.

Radioactivity
Image: Henri Becquerel · Public domain · Wikimedia Commons

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First known
1896
Credited to
Henri Becquerel · Marie Curie · Pierre Curie
Built onX-rays1895
Led toNuclear fission1938

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Cite this entry
APA
The Epoch Institute. (2026). Radioactivity. In The Epoch Institute Encyclopedia. https://the-epoch-institute.org/encyclopedia/radioactivity
MLA
“Radioactivity.” The Epoch Institute Encyclopedia, The Epoch Institute, 2026, https://the-epoch-institute.org/encyclopedia/radioactivity. Accessed .
Chicago
The Epoch Institute. “Radioactivity.” The Epoch Institute Encyclopedia. 2026. https://the-epoch-institute.org/encyclopedia/radioactivity.
Harvard
The Epoch Institute (2026) ‘Radioactivity’, The Epoch Institute Encyclopedia. Available at: https://the-epoch-institute.org/encyclopedia/radioactivity (Accessed: ).

Last reviewed October 2026Random entry ↻