DISCOVERY OF RADIOACTIVE ELEMENTS
reading this section you will be able to do the following:
why Becquerel earned the recognition of being awarded the 1903
Nobel Prize for physics.
what Becquerel found out about the element uranium.
the discovery of radioactive elements
to Roentgen's discovery of X-rays, in 1896 a French scientist
Henri Becquerel was experimenting with a uranium compound. While
investigating the properties of fluorescent minerals, it was Becquerel
who discovered that certain types of atoms disintegrate by themselves.
When working on the principles of fluorescence, he utilized photographic
film to record fluorescence of various minerals when exposed to
One of the minerals Becquerel
worked with was a uranium compound. The experiment normally consisted
of wrapping some photographic film in light proof paper, placing
a piece of fluorescent uranium on top of the film, and leaving
them in the sun. One day, after preparing the experiment, it was
too cloudy to expose his samples to direct sunlight, so he stored
the uranium compound and the film in a drawer. A couple of days
later, he decided to develop this film anyway, and discovered
an image of the uranium sample on the film. Becquerel questioned
what would have caused this. He knew he had wrapped the film tightly
in light proof paper, so the image was not due to stray light.
In addition, he noticed
that only the film that was in the drawer with the uranium compound
had an image on it. Becquerel concluded that the uranium compound
gave off something invisible that could penetrate heavy paper
and affect photographic film. Becquerel continued to test many
samples of compounds and determined that the source of the invisible
something was the element uranium. This invisible something was
named radiation, and it was determined that an element
that gives off radiation is a radioactive element. Today,
we know uranium as one of the radioactive elements. For his discovery
of radioactivity, Becquerel was awarded the 1903 Nobel Prize for
Becquerel discovered the radioactive properties of uranium when
he stored a piece with some film and notched an image on the
was named a radioactive element because if gives off something
that is invisible to the human eye called radiation.