Unformatted text preview: Chapter 4
The Atomic Nucleus Exam 1
Any questions? Which 1) of the following atoms would be the smallest?
Ca 2) K 3) Br 4) Kr 5) I Cathode Revisited In a high voltage cathode ray tube, more than an electron beam is produced new beam that is not deflected by electric or magnetic fields was produced A X-rays These They rays were discovered by Roentgen were named X because he did not know what they were These X-rays caused photographic paper to be exposed without having any light contact them lead the way for the discovery of new radiation and elements This Becquerel studied uranium. At first it appeared to be like X-rays and phosphorescence But the uranium exposed the photographic paper without needing sunlight Marie Curie also in the early 1900s she and her husband Pierre discovered two new radioactive elements, polonium and radium Radioactivity describes a materials ability to emit radiation Alpha particles Composed of two protons and two neutrons they are the heaviest of the radioactive products positive charge will be bent towards a negatively charged plate poor ability to penetrate Large Extremely materials Beta Particles These are basically just an electron that has been ejected from the nucleus like other electrons beta particles are attracted to a positively charged plate ability to penetrate materials Just Decent Gamma Rays These They rays are pure energy can travel a very long distance and penetrate thick materials are the most destructive types of These rays Protection Depending on the type of radiation different types of protection must be used For alpha a very thin sheet of paper or our skin For beta a thin sheet of metal or plastics For gamma a very thick sheet of a dense metal like lead Uses of radiation: Food preservatives Spices milk X-rays Radiation Is All Around Us We are exposed to radiation every day Where does most of this radiation come from? The majority of cosmic radiation is absorbed in the atmosphere But what happens as we move from sea level to higher altitudes? Which of the following professions would you expect to have the highest exposure to radiation? 1) laboratory researcher 2) X-ray technician 3) commercial airline pilot 4) coal miner 5) nuclear power plant technician Measures of Radiation Radiation is measured in several ways: curie or bequerel measure the amount of radiation emitted by a radioactive sample rad or gray measures the radiation dose absorbed by living tissue rem or sievert measures the biological risk of exposure to radiation (how harmful) The typical US citizen is exposed to 360 mrems a year
Most of this radiation comes from Radon a byproduct from uranium decay Radioactive Isotopes Why Lets do we use them? look at iodine... Iodine is one of the elements we consume in our normal diet It is mostly utilized in the thyroid But how can we see these iodine molecules? Iodine 131 that has been traced through the body to the thyroid Useful Radioactive Isotopes Phosphorous - 32 What makes an element radioactive? Important terms: Strong nuclear force a short ranged force that draws elemental particles together Electric force the force that pushes like charges away All nuclear particles feel the strong nuclear force Only charged particles (protons) feel the electrical repulsive force So larger atoms have more distance between the outer protons So as the nucleus gets larger it takes more and more neutrons to keep the protons from repulsing each other this causes a new problem... But Neutrons stabilize protons but do not like to be by themselves Alpha Decay Releases Two an alpha particle protons and two neutrons Beta Decay Releases an electron and converts a neutron to a proton Decay of Uranium Practice If P-32 is a beta emitter, what is the resultant element? 1) sulfur 2) phosphorous 3) electron 4) aluminum 5) chlorine Exam grades will be posted this afternoon along with homework 4. Homework 4 is due in a week before class begins ...
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