What Did Marie Curie Discover? Polonium, Radium and the Birth of a New Word

Marie Curie discovered two chemical elements, polonium and radium, both announced in 1898 together with her husband Pierre Curie, and the couple coined the word "radioactivity" to describe what those elements did. Her work showed that some atoms constantly give off energy, an idea that helped open the door to modern atomic physics, cancer radiotherapy and much more. It also made her the first woman to win a Nobel Prize, and later the first person to win two.

A girl from Warsaw who was not allowed to study

She was born Maria Salomea Skłodowska on 7 November 1867 in Warsaw, which was then part of the Russian Empire. She was the youngest of five children, and both of her parents were teachers. She was a brilliant student, but women could not enrol at the regular universities. Instead she attended the clandestine "Flying University", a secret network of classes in Warsaw that admitted women.

To get a real university education she made a pact with her older sister Bronisława. Maria worked as a governess for a landowning family and helped pay for Bronisława's medical studies in Paris; in return, Bronisława would later help her. It was a long, patient plan, and it worked.

Paris, physics and Pierre

In late 1891 she finally moved to Paris and enrolled at the University of Paris, studying physics, chemistry and mathematics. She earned a degree in physics in 1893 and a second degree in 1894. That same year she met the physicist Pierre Curie. They married on 26 July 1895 in Sceaux, without a religious ceremony, and became one of the most famous scientific partnerships in history.

Discovery one: polonium

By the late 1890s the Curies were investigating the strange rays given off by certain minerals, a field that the physicist Henri Becquerel, their future Nobel co-laureate, had also been exploring. Their working method was patient chemistry: break a mineral down, measure the rays from each part, and follow the signal to its source.

In July 1898 the Curies announced the first of those hidden substances. Marie named it polonium, after her native Poland. The choice was political. Poland had been partitioned among neighbouring empires and did not exist as an independent state, and she hoped the name would draw attention to that fact.

Discovery two: radium

On 21 December 1898 the Curies identified a second new element in a sample of pitchblende, a uranium-rich ore, from Jáchymov in Bohemia. They named it radium, from the Latin radius, meaning "ray", because of the energy it gave off as rays.

Proving that radium really existed was another matter. It occurs in tiny amounts, so years of exhausting chemical work were needed to separate even small quantities. In 1910 Marie Curie and the chemist André-Louis Debierne finally isolated radium as a pure metal, by electrolysis of radium chloride.

Inventing the word "radioactivity"

Just as important as the elements was the concept. The Curies coined the term "radioactivity" for the ability of certain substances to emit radiation on their own. Today the word is so common that it is easy to forget that someone had to invent it.

Her influence lives on in units and names. The curie, an old unit of radioactivity, was originally defined by the activity of one gram of radium-226, and element 96 was later named curium.

Two Nobel Prizes, one tragedy

In 1903 Marie, Pierre and Henri Becquerel shared the Nobel Prize in Physics, and Marie became the first woman ever to receive a Nobel Prize. Three years later disaster struck. On 19 April 1906 Pierre was killed in a Paris street when he was struck by a horse-drawn vehicle.

Marie carried on. She took over Pierre's chair and became the first woman to hold a professorship at the University of Paris. In 1911 she won the Nobel Prize in Chemistry, for the discovery of radium and polonium and the isolation of radium. She remains one of only two people, with Linus Pauling, to win Nobel Prizes in two different fields.

The same year, the French press attacked her over her relationship with the physicist Paul Langevin, and a mob gathered outside her home. The chair of the Nobel committee even tried to discourage her from attending the ceremony. She went anyway.

Radium at war

When the First World War began, Curie turned her knowledge into practical help. She developed mobile X-ray units, nicknamed petites Curies ("little Curies") to serve field hospitals close to the fighting, and she directed the Red Cross radiology service. She also led the Curie Laboratory at the new Radium Institute in Paris, built in 1914, which later produced several more Nobel laureates, including her daughter Irène and Irène's husband Frédéric Joliot-Curie.

The price of discovery

The dangers of radiation were poorly understood at the time. Radium was even added to cosmetics, soaps and drinks, and factory workers who painted watch dials with radium paint suffered sores, anaemia and bone cancer. Curie herself died on 4 July 1934, aged 66, of aplastic anaemia, most likely caused by her long exposure to radiation. Her notebooks are still so radioactive that they are expected to remain so for well over a thousand years.

She deliberately did not patent the radium-isolation process, so that other researchers could work freely. In 1995 her remains were moved to the Panthéon in Paris, making her the first woman honoured there on her own merits.

Learn with Marie Curie: English phrases for discovery

Phrase	Meaning	Example
to break new ground	to do something nobody has done before	Her research broke new ground in physics.
to coin a term	to invent a new word or phrase	The Curies coined the term "radioactivity".
to pave the way	to make later progress possible	Her work paved the way for radiotherapy.
against all odds	despite huge difficulties	Against all odds, she studied in Paris.
to carry on	to continue after a difficulty	After Pierre's death, she carried on.

Try this: Marie Curie made a long-term pact with her sister. Write a three-sentence "pact" with yourself in English about your language learning, using "I will…", "In return…" and "By the end of the year…".