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Becquerel Chemistry Project

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angela bleke

on 28 February 2013

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Transcript of Becquerel Chemistry Project

Haley Thomas, Miranda Solveson, Angela Bleke, and Maggie Schoenecker Becquerel His Atomic Theory
1. All matter is made of atoms.
Atoms are indivisible and indestructible.
2. All atoms of a given element
are identical in mass and properties
3. Compounds are formed by a
combination of two or more different kinds of atoms.
4. A chemical reaction is a
rearrangement of atoms. John Dalton: 1766-1844 1845-1923 German physicists, and discovered x rays in 1895. Also received the first nobel prize for physics in 1901. He had been conducting research on the phenomena of cathode rays when he accidentally put a piece of cardboard covered with fluorescent mineral near the experimental set and he noticed it started to glow in the dark when the cathode ray source was turned on. while he was experimenting, he observed that certain rays were emitted during the passing of the current through a discharge tube. He discovered that if the vacuum tube, used for experiments with cathode rays, was covered tightly with thin, black cardboard and placed in a darkened room, bright glow was observed during each discharge on a screen covered with fluorescent barium platinum cyanide (placed near the device). It did not matter which side (the one covered with the mineral or the other one) of the screen faced the device. Fluorescence occurred even when the screen was placed two meters from the vacuum tube.He generated the very first "roentgenogram" by developing the image of his wife's hand and analyzed the transparency as showed by her bones, skin and her wedding ring. Based on his subsequent research and experiments, he declared that X-ray beams are produced by the impact of cathode rays on material objects. Roentgen showed that under the influence of X rays not only barium platinum cyanide but also other substances fluoresce: fluorescent compounds of calcium, uranium glass, plain glass, calcite, rock-salt. Also photographic plates are sensitive to X rays. On the other hand retina of an eye is not sensitive to them. Roentengen 1852-1908 Becquerel was awarded the 1903 Nobel Prize for his discoveries. In Becquerel’s experiment he was conducting an experiment which started with the exposure of a uranium-bearing crystal to sunlight. Once the crystal had sat in the sunshine for a while, he placed it on a photographic plate. As he had anticipated, the crystal produced its image on the plate. Becquerel theorized that the absorbed energy of the sun was being released by the uranium in the form of x-rays. Further testing had to wait because the next couple days were cloudy, so Becquerel placed the photographic plate and sample of uranium in a drawer for when the sky cleared up. When it did clear up he got all of his gear out of the drawer and he was surprised to find that the crystal had left a clear, strong image on the photographic plate. What Becquerel had discovered was that a piece of mineral which contained uranium could produce it's image on a photographic plate in the absence of light. What he had discovered was radioactivity. He attributed this held the credit of the radioactivity to spontaneous emission by the uranium. Becquerel Shortly after the discovery of radioactivity, Rutherford turned to studying the particles emitted by uranium and its compounds. He classified radiation into three types: Alpha, beta, and gamma, according to how they were deflected in a magnetic field. Rutherford Marie and Pierre Curie began studying radioactivity in the 1890’s and measured the results of the release of electrons from the nucleus that few people had ever heard about. Marie wanted to research about the much ignored Uranium rays. This appealed to Marie immensly. The Paris Municipal School of Industrial Physics and Chemistry let Marie use a crowded, damp storeroom there as a lab to work in. This is where Pierre, her husband was a professor of physics. Prior to Marie conducting an experiment, Pierre and his older brother, Jacques invented a new kind of electrometer. AN electrometer is a device used for measuring extremely low electrical currents. Marie put the Curie electrometer to the test. She used it in measuring the faint currents that could pass through the air that has been bombarded with uranium rays. The moist air in the storeroom tended to dissipate the electric charge, but Marie managed to make reproducible measurements. With numerous experiments, Marie confirmed Becquerel’s observation that the electrical effects of uranium rays are constant, regardless of whether the uranium was solid or pulverized, pure in a compound, wet or dry, or exposed to heat or light. Her studies also validated that the minerals with a higher proportion of uranium emitted the most intense rays. The Curies **Based on our data, the magnet had little to no effect to any of the nuclides used. There was one exception to this; the green nuclide. In the box alone, there were 27 beeps, but when the magnets were there, the green nuclide only had 11 beeps. Other than the green nuclide, all of the other nuclides stayed the same in terms of radioactivity. Experiment Q&A... Plum Pudding Model 3 thing required to generate an xray: a source of electrons, a means of accelerating the electrons at high speeds, and a target material to receive the impact of the electrons and interact with them. *Vocabulary:

Cathode rays : A cathode ray tube is a type of vacuum tube which contains a source of electrons and a fluorescent screen, with some means to accelerate and deflect the electron beam. Cathode ray tubes commonly are used to form images on the fluorescent screen.



Fluorescence : Fluorescence is luminescence that occurs where the energy is supplied by electromagnetic radiation, usually ultraviolet light. The energy source kicks an electron of an atom from a lower energy state into an "excited" higher energy state; then the electron releases the energy in the form of light (luminescence) when it falls back to a lower energy state.



Ultraviolet Radiation : Ultraviolet radiation is electromagnetic radiation or light having a wavelength greater than 10 nm but less than 400 nm. Ultraviolet radiation has a wavelength longer than that of x-rays but shorter than that of visible light. Ultraviolet is energetic enough to break some chemical bonds.



X rays : Invisible electromagnetic radiation with wavelengths shorter than visible light. X rays are produced when high energy charged particles collide with other charged particles or with atoms. (X-rays are a form of electromagnetic radiation which are emitted when matter is bombarded with fast electrons.) Vocabulary:



Photographic Plate: a flat sheet of metal or glass on which a photographic image can be recorded.


Radioactivity: Radioactivity is the spontaneous emission of radiation in the form of particles or high energy photons resulting from a nuclear reaction. Three Types of Radioactivity:

1. Alpha Radiation-- Aplpha radiation have the least penetrating power, move at a slower velocity than the other types, and are deflected slightly by a magnetic field in a direction that indicates a positive charge.

2. Beta Radiation-- Beta Radiation are more penetrating than alpha rays, move at a very high speed, and are deflected considerably by a magnetic field in a direction that indicates a negative charge; analysis shows that beta rays are high-speed electrons.

3. Gamma Radiation-- Gamma radiation have very great penetrating power and are not affected at all by a magnetic field. They move at the speed of light and have a very short wavelength (or high frequency); thus they are a type of electromagnetic radiation. MARIE’S HYPOTHESIS: the emission of rays by uranium compounds could be an atomic property of the element uranium. This is something built into the very structure of its atoms. -This simple hypothesis would prove to be revolutionary. Nobody grasped the complex inner structure or the immense energy stored in atoms. Marie and Pierre Curie were not convinced that radioactive energy came from within atoms. Marie’s real achievement was to cut through the complicated and obscure observations with a crystal-clear analysis of the set of conclusions that, however unexpected, were logically possible. Marie tested all the known elements in order to determine if the other elements (or minerals) would truly make air conduct electricity better. She also wanted to find out if uranium alone could do this. Marie was assisted by a number of chemists who donated a variety of mineral samples. Again, the emission appeared to be an atomic property. To describe the behavior of uranium and theorem she invented the word “radioactivity”. This word was based on the Latin word for ray! Alpha radiation consists of particles rather than rays. Alpha particles are helium nuclei, containing two protons and two neutrons. By particle physics standards, alpha particles have a relatively large mass and nuclear cross section. Nuclear physicists use the cross section to measure how likely a particle is to interact with matter. The large cross section makes alpha radiation both fairly safe and fairly lethal. Because alpha particles easily interact with matter, they are easily absorbed. These particles therefore have a short range and little penetrating power. Paper or ordinary indoor clothing can block most alpha particles. Hence it is quite easy to shield radioactive alpha sources. Beta radiation consists of particles rather than rays. Beta particles are either electrons or positrons, which are the antimatter particles corresponding to electrons. Beta radiation has a little more range and penetrating power than alpha radiation. A sheet of aluminum a few millimeters thick is, however, enough to block most beta particles. As for alpha radiation, beta radiation is most dangerous when one eats or drinks a beta decay source. Like light, radio waves, and X-rays, gamma rays are a type of electromagnetic wave. With the highest energy on the electromagnetic spectrum, gamma rays have much more penetrating power than either alpha or beta radiation and can pass through concrete walls. It takes several centimeters of lead to block gamma rays. The high energy and penetrating power make gamma radiation dangerous. Vocabulary:

Magnetic Field: A field of force
associated with changing electric fields, as when electric charges are in motion. Magnetic
fields exert deflective forces on moving electric charges.

Antimatter Particles: Every elementary
particle has a corresponding anti-particle, which is antimatter. Protons have anti-protons. Neutrons have anti-neutrons. Electrons have anti-electrons, which are common enough to have their own name: positrons. Particles of antimatter have a charge opposite that of their usual components. 2) How did Roentgen discover X-Rays? Why are they called X-rays?
Before Roentgen named it the x ray, he called it the “roentgenogram”. Because of its unknown character as to why it existed and all of its properties, this was called the ‘X-ray.” The name has stuck with it ever since. 3) What did Becquerel find out about the nature of radioactivity?
That the radioactive particles were emitted from substances. The substances did not gain the energy to emit things from external sources. 4) How did the Curies solidify what we know about radioactivity?
The Curies solidified what we know about radioactivity by measuring the results of the release of electrons from the nucleus. This helped to prove that the effects of uranium on the electrical current of the air is constant. Marie also tested all the known elements for the same property and found that only uranium atoms could do this. She found that the emission was an atomic property of only uranium. 5) Becquerel discovered that the mass/charge ratio of an alpha particle is 4000* greater than an electron but also found, from collision studies that it is about 8000* heavier than an electron. What does this imply?
This implies that the heavier the alpha particle the greater mass/charge ratio it will have. The alpha particle will always be significantly greater with a mass/charge ratio and in just mass than electrons. This also proves the conclusion that Rutherford came to that alpha particles move slower and have a lower penetration power because they are so large and heavy. 6) How did we know that the radiation was not part of the chemical properties of the uranium?
Because no matter whether the uranium is solid or pulverized, pure in a compound, wet or dry, or exposed to heat or light its releasing of particales stayed the same during Marie Curie's experiments and therefore kept the uranium's effect on the electricity of the air the same as well. 8) What happens to uranium or other elements after it radiates?
They breakdown and produce other elements. 7) JJ Thompson had to add energy to split the atom. How is that different than Becquerel?
Becquerel didn't have to supply any energy, because the uranium emitted its own energy on it own. 1) How is your experiment similar to Rutherford’s finding the ABC’s of radioactivity?
Our experiment was performed to see how many particles of each type of radiation could pass through different types of materials such as wood, paper, and foils. Rutherford's experiment was performed to see how many particles of each of the nuclides could pass through different metals, particularily gold. Now Let's Take A Look At Our Mock
Experiment...
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