Name Chemistry Essential question: How were the parts of the atom determined? Key Question: What role did the study of radioactivity play in learning more about atoms? Vocabulary: alpha particle fusion tracer artificial transmutation gamma ray transmutation beta particle half-life fission radioisotope Lesson 2: Radioactivity Part 1: Natural Radioactivity Definitions 1. The spontaneous of the nucleus of an atom with the emission of particles and/or radiation / 2. Naturally occurring radioactive elements start with atomic number higher than /. 3. The change of one element into another because of change in the nucleus 4. Natural radioactivity was discovered by Types of Emissions 1. The particle that is considered a helium nucleus because it consists of 2 protons and 2 neutrons 2. 3. The particle that is produced as a result of neutron disintegration into a proton and The particle identical to an electron except that it has a positive charge is a 4. Comparison of Emissions: Use Table O- Symbols Used in Nuclear Chemistry and p. 80
Property Alpha Particles Beta Particles Positrons Gamma Radiation Symbols Nature Speed Charge Mass (amu) Common Source Penetrating Power Ionizing Ability Decay Equations: Use Table N- Selected Radioisotopes 1. Alpha Decay: 226 Ra 4 He + 88 2 86 222 Rn Atomic Number:_ Mass Number: From Table N, find another alpha emitter and write the nuclear equation. 2. Beta Decay 234 Th 234 Pa + 90 91-1 0 e Atomic Number:_ Mass Number: From Table N, find another beta emitter and write the nuclear equation. 3. Positron Decay 37 Ca 37 K + 20 19 +1 0 e Atomic Number: Mass Number:
From Table N, find another positron emitter and write the nuclear equation. 4. Practice Equations: Write nuclear equations for the following: Rn-222: U-238: C-14: N-16: Ne-19:
Nuclear Transformations 1. Stability of Nuclei The nucleus of an atom, except for hydrogen, contain protons and neutrons. Most nuclei are stable. N Number of neutrons u equals twice the They fall in the m number of protons shown in the graph at the right. b e The _ of neutrons to protons r determines the stability of a nucleus. o Elements with atomic numbers greater than f are unstable due to the ratio of neutrons to protons. N e u t r o n Belt of Stability Equal numbers of protons and neutrons s Number of Protons 2. Half-Life: definition Use Table N- Selected Radioisotopes to find half-lives of nuclides and Table T- Important Formulas and Equations for the formula for half-life. a. What is the half-life of I-131? If you had 100 grams of I-131, how much would remain after 32 days? b. If you had a 40 gram sample of P-32, how much would be left after 42 days?
Decay Series Definition: 1. The series for U-238 involves 14 steps until the stable isotope is formed. 238 U Alpha 92 _ 83 _ 234 Th Beta> 234 Pa Beta> 234 U Alpha 230 Th 90 _ 91 214 _ < Alpha 92 218 Po <_ Rn <Alpha 84 90 Alpha _ 214 Po Alpha> Decay 210 _ Beta> > Po 84 Alpha> _ 2. The series for Po-218 involves 7 steps until a stable daughter nuclide is formed. a. Calculate the neutron to proton ratio for radioactive polonium-218. Record the answer to three decimal places. Answer: b. Complete the series from the radioactive parent, polonium-218, to the stable daughter. The types of are given in their correct sequence. Record the nuclear symbol of each daughter. Polonium-218 series (7 steps) alpha, beta, beta, alpha, beta, beta, alpha 1. 2. 3. 4. 5. 6. 7. c. Calculate the neutron to proton ratio for the stable daughter that ended the series you just completed. Again, report the answer to three decimal places. Answer: d. Compare the neutron to proton ratio of the radioactive parent, polonium-218, to the ratio of the stable daughter. Suggest a reason why the parent is unstable and the daughter is stable.
Part 2: Artificial Radioactivity 1. Definition: Discovered by _ in. 2. Particle Accelerators speed up charged particles to overcome the electrostatic forces and penetrate the of the target atom. See p. 808 in text. First particle accelerator ( ) was invented by. 3. Nuclear Reactions release millions of times more energy than ordinary chemical reactions. Albert Einstein s helped explain how mass can be converted into energy. A. Nuclear fission: Used in nuclear reactors to produce electrical energy from splitting. Produces radioactive wasters such as _ Fission of U-235: B. Nuclear Fusion:_ Sample reaction: Fusion reactors, while not in use yet, offer the best method for producing great amounts of energy. Fuels: from sea water and made from a nuclear reaction High energy requirement: challenges scientists and engineers
Uses of Radioisotopes 1. Chemical tracers: any radioisotope use to follow the path of a material in a system. Examples: is used to trace the uptake of phosphorus from fertilizers by plants is used to map the path of carbon in metabolic processes 2. Industrial applications: isotopes are absorbed by different materials. The of plastic wrap or aluminum foil can be determined. 3. Medical Applications: to diagnose and treat diseases radioisotopes must have a half-life and be quickly eliminated from the body Iodine-131: Cobalt-60: Strontium-87:_ Technetium-99: Gallium-67: 4. Irradiation of Foods: gamma radiation is used to kill in spices, produce, and meats. The food has a longer shelf life and is safer. 5. Dating: Carbon-14 is used to date Uranium-238 is used to date. The ratio of U-238:_ indicates how old a geological formation is. Radiation Risks 1. Mutations: 2. Cancers:_ 3. Wastes from nuclear power plants: 4. Accidents at nuclear power plants: