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One of Marie Curie’s most influential contributions to science was her research concerning Becquerel radiation. In 1896, after the German physicist Wilhelm Roentgen discovered the existence of x-rays the previous year, a French physicist, Henri Becquerel, discovered that any compound containing uranium would fog up light sensitive photographic plates regardless of the condition of the uranium. In the wake of Roentgen’s discovery, Becquerel was met with little attention in the scientific community. However, Marie Curie (then Marie Sklodowska) was interested in Becquerel’s uranium discovery and took it upon herself to study the phenomenon in more detail. Because of the lack of attention for Becquerel’s discovery, Marie did not have much to study in preparation for her research. This made it easy to begin her study immediately. In her storeroom laboratory at the Municipal School of Industrial Physics and Chemistry in Paris, she began to study the radioactive properties of uranium using a piezoelectric electrometer, a device used to measure electric current invented 15 years earlier by Pierre Curie and his brother (right). Throughout many different tests using uranium under varying conditions and in various compounds, the difference in radioactivity levels differed solely depending on the amount of uranium. After testing with all known elements at the time, thorium was the only other element that replicated this phenomenon. Her extensive variation of scientific variables with no change in radiation levels led Marie to hypothesize that radiation was not caused by the form of uranium or its surroundings, but that there was something in its atomic makeup that made it radiate. This hypothesis would become revolutionary, changing scientific conception of the universe forever. It disproved the widely accepted concept that atoms were the smallest units of mass.
As the scientific community understands today, atoms are composed of a nucleus, formed from protons and neutrons, and surrounding electrons. The amount of protons defines the type of atom. The Becquerel radiation of uranium and other substances, thanks to Marie’s contribution to atomic physics, is now known to be the emission of two protons and two neutrons. This is a highly energized helium nucleus called an alpha particle. This process is shown below. The reason for its emission is that certain elements have too low a ratio of neutrons to protons, making them unstable and ready to emit alpha particles in order to find an acceptable ratio. Alpha particles are not dangerous in small periods of exposure because both clothes and the layer of dead skin on your body can not be penetrated easily by the large particles. However, if alpha radiation is worked with for long periods of time without proper protection or a substance that emits alpha particles is ingested, there can be an effect on tissue within the body, heightening the risk of cancer. Unfortunately for Marie, she was a martyr as her work is what would uncover this fact
As the scientific community understands today, atoms are composed of a nucleus, formed from protons and neutrons, and surrounding electrons. The amount of protons defines the type of atom. The Becquerel radiation of uranium and other substances, thanks to Marie’s contribution to atomic physics, is now known to be the emission of two protons and two neutrons. This is a highly energized helium nucleus called an alpha particle. This process is shown below. The reason for its emission is that certain elements have too low a ratio of neutrons to protons, making them unstable and ready to emit alpha particles in order to find an acceptable ratio. Alpha particles are not dangerous in small periods of exposure because both clothes and the layer of dead skin on your body can not be penetrated easily by the large particles. However, if alpha radiation is worked with for long periods of time without proper protection or a substance that emits alpha particles is ingested, there can be an effect on tissue within the body, heightening the risk of cancer. Unfortunately for Marie, she was a martyr as her work is what would uncover this fact
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A second and more prestigious achievement of Marie Curie’s was the discovery of polonium and radium. While studying the radioactivity of the uranium ore called pitchblende, she found it more radioactive than pure uranium. To Marie, the only explanation could be that there were still undiscovered radioactive elements. After rigorous chemical separation processes, developed by Marie and Pierre themselves, they were left with two radioactive portions of bismuth and barium extracted from the pitchblende. Neither bismuth nor barium are radioactive so they must contain the new elements, polonium in the bismuth and radium in the barium. Unfortunately, polonium was unable to be extracted, for it has a half life (the time it takes for half of a substance to “disappear” due to its radioactive properties) of only 138 days and it is extremely similar to bismuth on a chemical level. Radium, on the other hand, was extracted through a technique called fractional crystallization. When water is heated to boiling, it can dissolve a certain amount of salt (salt being a chemical structure of repeating pattern, left). As the water is cooled, the water will allow less of the salt to be dissolved, therefore causing the salt to come out of solution and form solid crystals. Some salts can be more easily dissolved than others, making one chemical in solution more likely to form crystals. In this case, the salt radium chloride will form into crystals and barium chloride will stay in solution when water is cooled. Radium chloride can then be extracted after multiple performances of this technique.
After her discovery and study of polonium and radium, Marie Curie continued on to experiment with the medicinal effects of radium and radiotherapy. Through her and her husband’s studies, they found that radioactivity could help as a treatment for some cancers. However, they also found that there were harmful, carcinogenic side effects caused by overexposure to radioactive elements. This discovery may have been too late, however, as Marie Curie died in 1934 from leukemia.