Curie, Marie

Curie, Marie (1867-1934), Polish-born French chemist who, with her husband Pierre Curie, was an early investigator of radioactivity. Radioactivity is the spontaneous decay of certain elements into other elements and energy. The Curies shared the 1903 Nobel Prize in physics with French physicist Antoine Henri Becquerel for fundamental research on radioactivity. Marie Curie went on to study the chemistry and medical applications of radium. She was awarded the 1911 Nobel Prize in chemistry in recognition of her work in discovering radium and polonium and in isolating radium

Marie Curie's maiden name was Maria Skłodowska, and her nickname while growing up was Manya. She was born in Warsaw at a time when Poland was under Russian domination after the unsuccessful revolt of 1863. Her parents were teachers, but soon after Manya (their fifth child) was born, they lost their teaching posts and had to take in boarders. Their young daughter worked long hours helping with the meals, but she nevertheless won a medal for excellence at the local high school, where the examinations and some classes were held in Russian. No higher education was available to women in Poland at that time, so Manya took a job as a governess. She sent part of her earnings to Paris to help pay for her older sister's medical studies. Her sister qualified as a doctor and married a fellow doctor in 1891. Manya went to join them in Paris, changing her name to Marie. She entered the Sorbonne (now the Universities of Paris) and studied physics and mathematics, graduating at the top of her class. In 1894 she met the French chemist Pierre Curie, and they were married the following year.

From 1896 the Curies worked together on radioactivity, building on the results of German physicist Wilhelm Roentgen (who had discovered X rays) and Henri Becquerel (who had discovered that uranium salts emit similar radiation). Marie Curie discovered that the metallic element thorium also emits radiation and found that the mineral pitchblende emitted even more radiation than its uranium and thorium content could cause. The Curies then carried out an exhaustive search for the substance that could be producing the radioactivity. They processed an enormous amount of pitchblende, separating it into its chemical components. In July 1898 the Curies announced the discovery of the element polonium, followed in December of that year with the discovery of the element radium. They eventually prepared 1 g (0.04 oz) of pure radium chloride from 8 metric tons of waste pitchblende from Austria. They also established that beta rays (now known to consist of electrons) are negatively charged particles.

In 1906 Marie took over Pierre Curie’s post at the Sorbonne when he was run down and killed by a horse-drawn carriage. She became the first woman to teach there, and she concentrated all her energies into research and caring for her daughters. The Curies’ older daughter, Irene, later married Frédéric Joliot and became a famous scientist and Nobel laureate herself (see Irene Joliot-Curie; Frédéric Joliot-Curie). In 1910 Marie worked with French chemist André Debierne to isolate pure radium metal. In 1914 the University of Paris built the Institut du Radium (now the Institut Curie) to provide laboratory space for research on radioactive materials.

At the outbreak of World War I in 1914, Marie Curie helped to equip ambulances with X-ray equipment, which she drove to the front lines. The International Red Cross made her head of its Radiological Service. She and her colleagues at the Institut du Radium held courses for medical orderlies and doctors, teaching them how to use the new technique. By the late 1920s her health began to deteriorate: Continued exposure to high-energy radiation had given her leukemia. She entered a sanatorium at Haute Savoie and died there on July 4, 1934, a few months after her daughter and son-in-law, the Joliot-Curies, announced the discovery of artificial radioactivity.

Throughout much of her life Marie Curie was poor, and she and her fellow scientists carried out much of their work extracting radium under primitive conditions. The Curies refused to patent any of their discoveries, wanting them to benefit everyone freely. The Nobel Prize money and other financial rewards were used to finance further research. One of the outstanding applications of their work has been the use of radiation to treat cancer, one form of which cost Marie Curie her life.

Polonium

Polonium, symbol Po, rare, radioactive metallic element. Polonium is in group 16 (or VIa) of the periodic table (see Periodic Law). Its atomic number is 84.

The first element to be discovered by means of its radioactivity, polonium was found in pitchblende in 1898 by the French chemist Marie Curie, who named it for her native country, Poland. Polonium is one of the elements in the uranium-radium series of radioactive decay, the first member of which is uranium-238. Polonium occurs in radium-containing ores and is found in isotopic forms with mass numbers ranging from 192 to 218. Polonium 209 (also called radium-F), the only naturally occurring isotope, has a half-life of 138 days. Polonium melts at about 254° C (about 489° F), boils at about 962° C (about 1764° F), and has a specific gravity of 9.4.

Because most polonium isotopes disintegrate by emitting alpha particles, the element is a good source of pure alpha radiation. It is also used in nuclear research with elements such as beryllium that emit neutrons when bombarded by alpha particles. In printing and photography equipment, polonium is used in devices that ionize the air to eliminate accumulation of electrostatic charges.

Radium

I INTRODUCTION

Radium (Latin radius,”ray”), symbol Ra, chemically reactive, silvery white, radioactive metallic element. In group 2 (or IIa) of the periodic table (see Periodic Law), radium is one of the alkaline earth metals. The atomic number of radium is 88.

Radium was discovered in the ore pitchblende by the French chemists Marie Curie and Pierre Curie in 1898. They discovered that the ore was more radioactive than its principal component, uranium, and they separated the ore into many chemical fractions in order to isolate the unknown sources of radioactivity. One fraction, isolated by use of bismuth sulfide, contained a strongly radioactive substance that the Curies showed was a new element, polonium. A highly radioactive barium-chloride fraction was treated to remove the radioactive substance, which was discovered to be a new element, radium.

II PROPERTIES AND OCCURRENCE

Radium-226 metal melts at about 700° C (about 1292° F), and has a specific gravity of 5.5. The element oxidizes immediately upon exposure to air. The element is used and handled in the form of radium chloride or radium bromide and practically never in the metallic state.

Radium is formed by the radioactive disintegration of uranium and is consequently found in all uranium ores. Radium is present in uranium ore to the extent of 1 part of radium to 3 million of uranium. It is extracted from the ore by the addition of a compound of barium that acts as a “carrier.” The chemical properties of radium are similar to those of barium, and the two substances are removed from the other components of the ore by precipitation of barium and radium sulfate. The sulfates are converted into carbonates or sulfides, which are then dissolved in hydrochloric acid. The radium is separated from the barium as the end result of successive crystallizations of the chloride solutions.

Of the isotopes of radium, ranging in mass number from 206 to 232, the most abundant and most stable is the isotope of mass 226. Radium-226 is formed by the radioactive disintegration of the thorium isotope of mass 230, which is the fourth successive isotope in the decay series starting with uranium-238. The half-life of radium-226 is 1620 years. It emits alpha particles, forming the gas radon.

III USES

Radiation from radium has a harmful effect upon living cells, and radium burns are caused by overexposure to the rays. Cancerous cells, however, are often more sensitive to radiation than normal cells, and such cells may be killed without seriously injuring healthy tissue by controlling the intensity and direction of the radiation. Radium is now used in the treatment of only a few kinds of cancer; radium chloride or radium bromide is enclosed in a sealed tube and inserted in the diseased tissue. When a radium salt is mixed with a substance such as zinc sulfide, the substance is caused to luminesce by the bombardment of the alpha rays emitted by the radium. Small amounts of radium were once used in the production of luminous paint, which was applied to clock dials, doorknobs, and other objects, to make them glow in the dark.

Curie, Marie

b. Nov. 7, 1867, Warsaw, Pol., Russian Empire

d. July 4, 1934, near Sallanches, France

née MARIA SKLODOWSKA

Marie Curie

Polish-born French physicist famous for her work on radioactivity and twice a winner of the Nobel Prize. With Henri Becquerel and her husband, Pierre Curie, she was awarded the 1903 Nobel Prize for Physics. She was then sole winner of the 1911 Nobel Prize for Chemistry.

From childhood she was remarkable for her prodigious memory, and at the age of 16 she won a gold medal on completion of her secondary education at the Russian lycée. Because her father, a teacher of mathematics and physics, lost his savings through bad investment, she had to take work as a teacher and, at the same time, took part clandestinely in the nationalist "free university," reading in Polish to women workers. At the age of 18 she took a post as governess, where she suffered an unhappy love affair. From her earnings she was able to finance her sister Bronia's medical studies in Paris, on the understanding that Bronia would in turn later help her to get an education.

In 1891 Marie Sklodowska went to Paris and began to follow the lectures of Paul Appel, Gabriel Lippmann, and Edmond Bouty at the Sorbonne. There she met physicists who were already well known--Jean Perrin, Charles Maurain, and Aimé Cotton. Sklodowska worked far into the night in her students'-quarter garret and virtually lived on bread and butter and tea. She came first in the licence of physical sciences in 1893. She began to work in Lippmann's research laboratory and in 1894 was placed second in the licence of mathematical sciences. It was in the spring of this year that she met Pierre Curie.

Their marriage (July 25, 1895) marked the start of a partnership that was soon to achieve results of world significance, in particular the discovery of polonium (so called by Marie in honour of her native land) in the summer of 1898, and that of radium a few months later. Following Henri Becquerel's discovery (1896) of a new phenomenon (which she later called "radioactivity"), Marie Curie, looking for a subject for a thesis, decided to find out if the property discovered in uranium was to be found in other matter. She discovered that this was true for thorium at the same time as G.C. Schmidt did.

Turning to minerals, her attention was drawn to pitchblende, a mineral whose activity, superior to that of pure uranium, could only be explained by the presence in the ore of small quantities of an unknown substance of very high activity. Pierre Curie then joined her in the work that she had undertaken to resolve this problem and that led to the discovery of the new elements, polonium and radium. While Pierre Curie devoted himself chiefly to the physical study of the new radiations, Marie Curie struggled to obtain pure radium in the metallic state--achieved with the help of the chemist A. Debierne, one of Pierre Curie's pupils. On the results of this research Marie Curie received her doctorate of science in June 1903 and, with Pierre, was awarded the Davy Medal of the Royal Society. Also in 1903 they shared with Becquerel the Nobel Prize for Physics for the discovery of radioactivity.

The birth of her two daughters, Irène and Ève, in 1897 and 1904 did not interrupt Marie's intensive scientific work. She was appointed lecturer in physics at the École Normale Supérieure for girls in Sèvres (1900) and introduced there a method of teaching based on experimental demonstrations. In December 1904 she was appointed chief assistant in the laboratory directed by Pierre Curie.

The sudden death of Pierre Curie (April 19, 1906) was a bitter blow to Marie Curie, but it was also a decisive turning point in her career: henceforth she was to devote all her energy to completing alone the scientific work that they had undertaken. On May 13, 1906, she was appointed to the professorship that had been left vacant on her husband's death; she was the first woman to teach in the Sorbonne. In 1908 she became titular professor, and in 1910 her fundamental treatise on radioactivity was published. In 1911 she was awarded the Nobel Prize for Chemistry, for the isolation of pure radium. In 1914 she saw the completion of the building of the laboratories of the Radium Institute (Institut du Radium) at the University of Paris.

Throughout World War I, Marie Curie, with the help of her daughter Irène, devoted herself to the development of the use of X-radiography. In 1918 the Radium Institute, the staff of which Irène had joined, began to operate in earnest, and it was to become a universal centre for nuclear physics and chemistry. Marie Curie, now at the highest point of her fame, and, from 1922, a member of the Academy of Medicine, devoted her researches to the study of the chemistry of radioactive substances and the medical applications of these substances.

In 1921, accompanied by her two daughters, Marie Curie made a triumphant journey to the United States, where President Warren G. Harding presented her with a gram of radium bought as the result of a collection among American women. She gave lectures, especially in Belgium, Brazil, Spain, and Czechoslovakia. She was made a member of the International Commission on Intellectual Co-operation by the Council of the League of Nations. In addition, she had the satisfaction of seeing the Curie Foundation in Paris develop and the inauguration in 1932 in Warsaw of the Radium Institute, of which her sister Bronia became director.

One of Marie Curie's outstanding achievements was to have understood the need to accumulate intense radioactive sources, not only for the treatment of illness but also to maintain an abundant supply for research in nuclear physics; the resultant stockpile was an unrivaled instrument until the appearance after 1930 of particle accelerators. The existence in Paris at the Radium Institute of a stock of 1.5 grams of radium in which, over a period of several years, radium D and polonium had accumulated, made a decisive contribution to the success of the experiments undertaken in the years around 1930 and in particular of those performed by Irène Curie in conjunction with Frédéric Joliot, whom she had married in 1926 (see Joliot-Curie, Frédéric and Irène). This work prepared the way for the discovery of the neutron by Sir James Chadwick and above all the discovery in 1934 by Irène and Frédéric Joliot-Curie of artificial radioactivity. A few months after this discovery Marie Curie died as a result of leukemia caused by the action of radiation. Her contribution to physics had been immense, not only in her own work, the importance of which had been demonstrated by the award to her of two Nobel Prizes, but because of her influence on subsequent generations of nuclear physicists and chemists.

In 1995 Marie Curie's ashes were enshrined in the Panthéon in Paris; she was the first woman to receive this honour for her own achievements.