7.2, 7.3 nearpod
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7.2, 7.3 nearpod

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7.2, 7.3 nearpod 7.2, 7.3 nearpod Presentation Transcript

  • 7.2 & 7.3 Nuclear Chemistry Radioactivity, Isotopes, Half-Life, Fission and Fusion.
  • Isotopes  Isotopes are atoms of the same element (same number of protons) that have different number of neutrons = different atomic mass, same atomic number.  Changing one element to another or one isotope to another is called Transmutation
  • Radiation  Radioactivity (aka Radioactive decay) is decomposition of a nucleus to form a different nucleus.  It is the release of high- energy particles and rays of energy which change the nucleus.  Radioactivity occurs because of isotopes wanting to become stable.
  • 7.2 Half Life  The time it takes for exactly one-half of a radio active sample to decay.  The shorter the half life the faster the decay.  The half-life for a given isotope is always the same.  Using the half-life scientists can calculate how much of a sample will be gone in a given amount of time.
  • Half life continued.  For example Strontium-90 starts with 10 g, after it’s first half-life (29 years) it becomes 5 g, second half-life (58 years) is 25 g, and so on.  A decay curve is a curved line on a graph that shows the rate at which the sample it is decaying. (x= number of half lives, y axis = how much remaining)
  • Isotope Pairs  Since, we know that when isotopes wish to become stable the change the particles in the nucleus through decay.  The sample before can change into a new element or isotope  The parent isotope is the one that decays and the daughter isotope is on of the products of the decay.
  • Video  The Origins Of Spiderman  Bit by radioactive spider effected by radioactive decay in a chemistry lab.
  • Quiz 1. What measurement can compare the rate of radioactive decay? a) Radiometric dating b) Radioactive microscope c) Decay curve 2. How many grams will be left over of a 100 g sample after 5 half lives? a) 10.5 b) 3.125 c) 20
  • 7.3 Nuclear Reactions  A nuclear reaction is when an atom changes by gaining or releasing particles or energy. (Can release subatomic particles and gamma rays)  This happens because of nucleus wanting stability by removing particles.  Bombarding a nucleus with alpha & beta particles, or gamma rays causes a reaction.  Scientists can cause a reaction by making nuclei unstable, causing it make a reaction.
  • Nuclear Fission  Nuclear fission is the splitting of a heavy nucleus into two lighter nuclei.  Heavy nuclei tend to unstable because of repulsive forces between their many protons.  The reactions releases a lot of energy along with the smaller nuclei and subatomic particles, from the binding force in the nucleus.  Fission is a large source for nuclear power from it’s energy.
  • Fission Continued  Some nuclei while undergoing fission can release subatomic particles, that can trigger more fission reactions this is called a chain reaction.  The number of fissions and the amount of energy released adds up quickly that can lead to violent explosions.  Fission is used for nuclear weapons, and nuclear power generators because of all the energy.  Since it difficult to control, power plants monitor and adjust constantly.  However, it produces radioactive waste that takes a long time to decay.
  • Nuclear Fusion  Nuclear fusion is when a small nucleus combines to produce a larger nucleus.  Other subatomic particles and energy is released.  Fusion occurs in the sun and other stars where pressure and high temperature causes isotopes of hydrogen to collide creating enormous amounts of energy.  There is no technology capable of using the energy from fusion reactions. Because it is so strong from high pressure and temperature, it is impossible to control.  It could be used in nuclear weapons as it is seen as strong.
  • Nuclear Equations  A nuclear equation is a set of symbols that indicates changes in the nuclei of atoms during nuclear reactions.  The sum of the mass numbers on each side of the equation stays the same.  The sum of the charges (atomic numbers) on each side of the equation stays the same.
  • Video • In this episode of spider man; A mad scientist, Doctor Pretorius, escapes from prison and plots widespread devastation with a nuclear weapon he calls "The Kingdom Come Device."
  • Quiz 1. Where does nuclear fusion occur? a) In the sun and other stars b) Under ground c) Inside a power plant 2. A nuclear reaction can release a) Gamma Rays b) Energy c) Subatomic Particles d) All of the above 3. A nuclear reaction is induced by a) alpha & beta particles , and gamma rays b) energy c) another atom 4. Nuclear fission releases a very large amount of…. a) energy b) electrons c) neutrons