Which scientist discovered natural radioactivity?

1. Analyze the question The question asks who discovered natural radioactivity, which is the spontaneous emission of radiation from certain elements. Look for the person who first observed it, not the person who studied it further.

2. Explain the concept Natural radioactivity is the spontaneous disintegration of unstable atomic nuclei, giving off alpha, beta, or gamma radiation. It happens without any outside influence.

3. Work through the options

• A. Enrico Fermi: He worked on nuclear reactions and built the first nuclear reactor (1942). He did not discover natural radioactivity.
• B. Henri Becquerel: In 1896 he found that uranium salts darkened photographic plates wrapped in black paper, even with no sunlight. This was the first observation of natural radioactivity.
• C. Marie Curie: She coined the term "radioactivity" and discovered the elements polonium and radium. She and Pierre Curie shared the 1903 Nobel Prize in Physics with Becquerel. However, she built on Becquerel's discovery.
• D. Michael Faraday: He is known for electromagnetic induction and electrolysis.
• E. Niels Bohr: He proposed the Bohr model of the atom.

4. Answer The discovery of natural radioactivity is credited to Henri Becquerel (1896), which is option B.

5. Exam tip Remember "B for Becquerel, B for Beginning". Becquerel began the story of radioactivity, and the Curies came next, isolating new radioactive elements. The SI unit of radioactivity, the becquerel (Bq), is named after him.