Chapter 17 · Radioactivity and Nuclear Chemistry
17.2The Discovery of Radioactivity
7 min · two checks
Predict
What did Becquerel and the Curies establish about uranium and similar elements?
The idea
- State what radioactivity is.
- Note that it produces new elements.
In 1896 Henri Becquerel found that uranium salts darken a photographic plate even in a drawer. Marie and Pierre Curie isolated further radioactive elements, including polonium and radium, and showed the activity belongs to particular atoms. Rutherford later sorted the rays by how they behave in a magnetic field and in air. None of this is a chemical glow. The nucleus is ejecting particles or energy and often becoming a different element.
That last fact broke the nineteenth-century idea that elements are unchangeable. In a nuclear equation, atomic numbers and mass numbers both have to balance, but the element on the left need not be the element on the right. The next section is the catalog of the common emissions.
Keep these
- Radioactivity is spontaneous nuclear emission.
- It does not require light or a chemical partner.
- One element can become another.