Which element was the first to be discovered by the Curies?

The first element discovered by the Curies was polonium, identified by Marie and Pierre Curie in July 1898.

The Curies were investigating why pitchblende, a uranium ore, was more radioactive than its uranium content could explain. After removing known substances, they found that the remaining material still emitted intense radiation. Chemical separation suggested the presence of an unknown element with properties resembling bismuth, which they named polonium.

Marie chose the name to honor Poland, her birthplace. Poland was then divided among the Russian, German, and Austro-Hungarian empires and did not exist as an independent state. Naming the element polonium drew international attention to the country’s political situation.

A common mix-up is radium, which the Curies announced later in 1898. Polonium was their first discovery; radium followed about five months later. Both discoveries came from painstaking work with pitchblende, and both helped establish radioactivity as a major field of scientific research.