Radioactivity at a Glance


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Image by Tel Asiado

Image by Tel Asiado

The Oxford Dictionary of Physics defines radioactivity as “the integration of certain atomic nuclei accompanied by the emission of alpha-particles (helium nuclei), beta-particles (electrons or positrons), of gamma radiation (short-wavelength electromagnetic waves).” What does that mean, in simple terms?

What is Radioactivity in Simple Terms?

Basically, radioactivity can be defined in terms of the atom, which is the smallest part of an element that can exist. Some atoms are unstable and break down into new atoms. When this happens, it gives off energy, referred to as radioactivity.

Who Discovered Radioactivity?

Radioactivity was not just “discovered” by a single person – in the late 1800s and early 1900s, multiple scientists made huge advances in the field.

French Physicist Henri Becquerel

French physicist Henri Becquerel (1852-1908) discovered radioactivity by accident.  In 1896, he was experimenting with a metal called uranium. He placed some in a drawer on top of a packet of photographic plates. When he later unwrapped and developed the plates, he found them to be blackened. Becquerel reasoned that radiation from the uranium had gone through the packet and reacted with the photographic plates. In effect, he had discovered “radio-activity”, a name that Marie Curie gave to the phenomenon.

  • The Curies – Pierre and Marie Curie

The famous Curies, physicist Pierre Curie (1859-1906) and Polish-born chemist Marie Curie (1867-1934), carried forward the work of Becquerel, seeking radioactive elements other than uranium in pitchblende. By 1898, the Curies discovered radium and polonium, although it took Marie Curie another four years to purify them.

Marie Curie invented the word ‘radioactivity.’  The element polonium is actually named after Poland, Marie Curie’s land of birth.

Nobel Laureates for Becquerel and the Curies

In 1903, Pierre and Marie Curie shared the Nobel Prize with Henri Becquerel for their work on radioactivity, “in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena…”

The Three Types of Radioactivity

Three types of radioactivity identified:

1. Alpha radiation – Alpha radiation is considered weak. It cannot even pass through paper.

2. Beta radiation – Beta radiation is stronger than alpha, but cannot pass through a sheet of wood.

3. Gamma radiation – Gamma radiation is the strongest. It can pass through wood, metal and people.

Sometime in 1900, British scientists Joseph Thomson and Ernest Rutherford discovered the alpha and beta radiation. The third type, gamma radiation, was discovered by French physicist Paul Villard.

Use of Radioactivity in Life

Used in harmless levels, and in carefully controlled doses, radioactivity treats cancer by killing cancer cells. This treatment is referred to as radiotherapy. Unfortunately, the treatment also kills healthy cells. The ability to isolate treatment of cancer cells without affecting healthy cells remains a challenge for future advances in technology.


Dr Mark Steer, Hayley Birch, Dr Andrew Impney, Editors. Science. London: Cassell Book, Octopus Publishing, 2008.

Ellyard, David. Who Discovered What When. Sydney: New Holland, 2005.

Oxford Dictionary of Physics, 5th Edition. Oxford: Oxford University Press, 2005 (Paperback).

Nobel Nobel Prize in Physics 1903 – Henri Becquerel, Pierre Curie, Marie Curie. Accessed May 10, 2011.

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