Henri Becquerel Discovers Radioactivity

The most important contribution I lertz made in this inaugural lecture was his prediction, based on his estimates of the energy sources available, that ultimately the Earth was completely dependent on the Sun for the light and heat it needed to support life. Of course, this picture would change after Henri Becquerel discovered radioactivity in 1896, and thus introduced the nuclear age of physics. 

FIGURE 17.2 Henri Becquerel discovered radioactivity when he noticed that an unexposed photographic plate left near some uranium oxide became fogged. This photograph shows one of his original plates annotated with his record of the event. 

Thus it was the physicists who took the next steps toward understanding the nature of matter. In 1896 the French physicist Henri Becquerel discovered radioactivity, and in 1897 the English physicist J. J. Thomson discovered the first subatomic particle, the electron. Subsequently, studies of the radiation emitted by radioactive atoms showed that these atoms emitted radiation of three different kinds, which were called alpha, beta, and gamma after the first three letters... 

Antoine Henri Becquerel discovered radioactivity using uranium salts. 

In 1896, the year before Thomson discovered the electron, Antoine Henri Becquerel discovered radioactivity. With this finding the long-assumed immutability of atoms became untenable. For the next decade and more, many physicists analyzed the decay products of atoms and by 1910 found that the decay products of radioactive atoms involved daughter atoms that were some-... 

Medieval alchemists spent years trying to convert other metals into gold without success. Years of failure and the acceptance of Dalton s atomic theory early in the nineteenth century convinced scientists that one element could not be converted into another. Then, in 1896 Henri Becquerel discovered radioactive rays (natural radioactivity) coming from a uranium compound. Ernest Rutherford s study of these rays showed that atoms of one element may indeed be converted into atoms of other elements by spontaneous nuclear disintegrations. Many years later it was shown that nuclear reactions initiated by bombardment of nuclei with accelerated subatomic particles or other nuclei can also transform one element into another—accompanied by the release of radiation (induced radioactivity). 

It was in Paris that she met her future husband and fellow researcher, Pierre Curie. Working with crude equipment in a laboratory that was primitive, even by the standards of the time, she and Pierre made a most revolutionary discovery only two years after Henri Becquerel discovered radioactivity. Radioactivity, the emission of energy from certain substances, was released from inside the atom and was independent of the molecular form of the substance. The absolute proof of this assertion came only after the Curies processed over one ton of a material (pitchblende) to isolate less than a gram of pure radium. The difficult conditions under which this feat was accomplished are perhaps best stated by Sharon Bertsch McGrayne in her book Nobel Prize Women in Science (Birch Lane Press, New York, p. 23) ... 

When Antoine Henri Becquerel discovered radioactivity in 1896, and Marie and Pierre Curie isolated radium and polonium in 1898, scientists were faced with a new phenomenon that was to disprove the ideas that atoms were indestructible, that no element could turn into another, and that the atoms of an element all weighed the same. In the hands of Ernest Rutherford and Frederick Soddy, radioactive... 

It was mentioned in Chapter 4 that Henri Becquerel discovered natural radioactivity in 1896, He noticed that salts of uranium were able to affect a photographic plate through layers of opaque material. Madame Curie (Marie Sldodowska Curie, 1867-1934, a Polish chemist working in Paris) then began a systematic study of radioactive substances, as the subject of her doctor s dissertation. She found natural pitchblende, mainly to be several times more active than puri-... 

Henri Becquerel discovered natural radioactivity by chance. Through research he found that radiation was emitted by any compound of uranium. He further found that the intensity of the radiation was unaffected by factors that normally influence the rates of chemical reactions the temperature, pressure, and type of uranium compound used. 

Edmond Becquerel was one of a family of scientists. His father, Antoine-Cesar, was professor of physics at the Museum d Histoire Naturelle, and his son, [Antoine-] Henri Becquerel, also a physicist, discovered the phenomenon of radioactivity (for which he received the Nobel Prize in 1903). 

The development of particle accelerators grew out of the discovery of radioactivity in uranium by Henri Becquerel in Paris in 1896. Some years later, due to the work of Ernest Rutherford and others, it was found that the radioactivity discovered by Becquerel was the emission o particles with kinetic energies o several MeV from uranium nuclei. Research using the emitted particles began shortly thereafter. It was soon realized that if scientists were to learn more about the properties of subatomic particles, they had to be accelerated to energies greater than those attained in natural radioactivity. 

Marie and Irene Curie, and their husbands, Pierre Curie and Frederic Joliot. Marie Curie (1867-1934) was born Maria Sklodowska in Warsaw, Poland, then a part of the Russian empire. In 1891 she emigrated to Paris to study at the Sorbonne, where she met and married a French physicist, Pierre Curie (1859-1906). The Curies were associates of Henri Becquerel, the man who discovered that uranium salts are radioactive. They showed that thorium, like uranium, is radioactive and that the amount of radiation emitted is directly proportional to the amount of uranium or thorium in the sample. 

Summary Radioactivity, the spontaneous decay of an unstable isotope to a more stable one, was first discovered by Henri Becquerel in 1896. Marie Curie and her husband expanded on his work and developed most of the concepts that are used today. 

In the last four years of the nineteenth century, scientists in France— notably Henri Becquerel and Marie and Pierre Curie—discovered that certain elements are radioactive. That is, their atoms naturally emit positively charged particles (alpha particles), negatively charged particles (beta particles), and energy (gamma radiation). 

At the end of the eighteenth century, scientists thought that pitchblende was a mixture of iron and zinc compounds. In 1789 Martin Heinrich Klaproth (1743—1817) discovered a new metallic element in a sample of pitchblende, which he named uranus after the recently discovered planet. Although what he actually discovered was the compound uranous oxide (UOj), it was adequate to establish him as the discoverer of uranium. For almost a century, scientists believed that the compound uranous oxide (UO ) was the elemental metal uranium. In 1841 Eugene-Melchoir Pefigot (1811—1890) finally isolated the metal uranium from its compound. Even so, no one knew that both the compounds and metal of uranium were radioactive until 1896, when Henri Becquerel (1852—1908) mistakenly placed apiece of potassium... 

In 1898 Marie Sklodowska Curie (1867-1934), while experimenting with thorium and uranium, coined the word radioactivity to describe this newly discovered type of radiation. She went on to discover polonium and radium. Madam Curie and her husband Pierre Curie (1859—1906), who discovered the piezoelectric effect, which is used to measure the level of radiation, and Henri Becquerel jointly received the 1903 Nobel Prize in Physics for their work on radioactivity. 

The element was discovered in the pitchblende ores by the German chemist M.S. Klaproth in 1789. He named this new element uranium after the planet Uranus which had just been discovered eight years earlier in 1781. The metal was isolated first in 1841 by Pehgot by reducing the anhydrous chloride with potassium. Its radioactivity was discovered by Henry Becquerel in 1896. Then in the 1930 s and 40 s there were several revolutionary discoveries of nuclear properties of uranium. In 1934, Enrico Fermi and co-workers observed the beta radioactivity of uranium, following neutron bombardment and in 1939, Lise Meitner, Otto Hahn, and Fritz Strassmann discovered fission of uranium nucleus when bombarded with thermal neutrons to produce radioactive iso-... 

Roentgen s discovery of x-rays stimulated great interest in this new form of radiation worldwide. Antoine Henri Becquerel (1852-1908) accidentally discovered the process of radioactivity while he was studying x-rays. Radioactivity involves the spontaneous disintegration of unstable atomic nuclei. Becquerel had stored uranium salts on top of photographic plates in a dark drawer. When Becquerel retrieved the plates, he noticed the plates contained images made by the uranium salts. Bec-querel s initial discovery in 1896 was further developed by Marie Curie (1867-1934) and Pierre Curie (1859-1906). Marie Curie coined the word radioactive to describe the emission from uranium. 

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