NUCLEAR CHANGES
Nuclear Radiation Radioactivity: process by which an unstable nucleus emits one or more particles or energy in the form of electromagnetic radiation. nuclear radiation: particles that are released from nucleus during radioactive decay. Chapter 9
ALPHA PARTICLES alpha particles consists of two protons and two neutrons Composed of He nucleus atom w/ +2 charge Least penetrating type of radiation Can be stopped by a sheet of paper
BETA PARTICLES beta particle: negatively charged electron emitted during certain types of radioactive decay Emitted at high speeds from nucleus
GAMMA PARTICLES gamma ray high-energy photon emitted by a nucleus during fission and radioactive decay. Most penetrating type of radiation Does not have a charge nor mass Neutron emission consists of matter that is emitted from an unstable nucleus. Neutrons are able to travel farther through matter than either alpha or beta particles.
Nuclear Fission Fission: process by which a nucleus splits into two or more fragments and releases neutrons and energy. Produces nuclei of lower mass than reactants Used to produce nuclear power (electricity) Produces extremely toxic waste Chapter 9
A. Nuclear Power Fission Reactors
A. Nuclear Power Fission Reactors Cooling Tower
A. F ission splitting a nucleus into two or more smaller nuclei some mass is converted to large amounts of energy
A. F ission chain reaction - self-feeding reaction
B. Fusion combining of two nuclei to form one nucleus of larger mass produces even more energy than fission occurs naturally in stars
A. Nuclear Power 235 U is limited danger of meltdown toxic waste thermal pollution Hydrogen is abundant no danger of meltdown no toxic waste not yet sustainable FISSIONFISSION FUSIONFUSION vs.
Nuclear Fusion Fusion: process in which light nuclei combine at extremely high temperature, forming heavier, more stable nuclei and releasing energy. Produces nuclei of higher mass than reactants Takes place in the sun. Helium is major by product Chapter 9
A. Nuclear Power Fusion Reactors (not yet sustainable) Tokamak Fusion Test Reactor Princeton University National Spherical Torus Experiment
A. Nuclear Power Fusion Reactors (not yet sustainable)
Beneficial Uses of Nuclear Radiation Smoke detectors small alpha-emitting isotope detects smoke particles in the air. Nuclear radiation is used to detect diseases. radioactive tracer: radioactive material that is added to a substance so that its distribution can be detected later.
Beneficial Uses of Nuclear Radiation Nuclear radiation therapy is used to treat cancer. Radiotherapy: treatment that uses controlled doses of nuclear radiation for treating diseases such as cancer. Agriculture uses radioactive tracers and radio-isotopes. understand biochemical processes in plants. Chapter 9
Possible Risks of Nuclear Radiation Nuclear radiation can ionize atoms. Ionization is a change in the number of electrons in an atom or molecule, causing the particle to be positively or negatively charged. Radiation sickness results from high levels of nuclear radiation. People working in radioactive areas wear a dosimeter, a device that measures the amount of nuclear radiation exposure. Studies have shown a relationship between exposure to high levels of nuclear radiation and cancer.
Possible Risks of Nuclear Radiation The risk depends upon the amount of radiation exposure. High concentrations of radon gas can be hazardous. Radon gas: colorless and odorless, produced by the decay of uranium-238 naturally occurs in soil and rock. Chapter 9
CHAPTER 24 Nuclear Energy II. Nuclear Reactions (p ) II. Nuclear Reactions (p )
A. F ission splitting a nucleus into two or more smaller nuclei some mass is converted to large amounts of energy
A. F ission chain reaction - self-feeding reaction
B. Fusion combining of two nuclei to form one nucleus of larger mass produces even more energy than fission occurs naturally in stars
CHAPTER 24 Nuclear Energy I. Radioactivity (p ) I. Radioactivity (p )
A. Definitions Radioactivity –emission of high-energy radiation from the nucleus of an atom Nuclide –nucleus of an isotope Transmutation –process of changing one element into another via nuclear decay
B. Types of Radiation Alpha ( ) –helium nucleus paper 2+ Beta-minus ( -) –electron 1- lead Gamma ( ) –high-energy photon 0 concrete
C. Nuclear Decay Why nuclides decay… –to obtain a stable ratio of neutrons to protons Stable Unstable (radioactive)
C. Nuclear Decay Alpha Emission Beta Emission TRANSMUTATION
D. Half-life Half-life (t ½ ) –time it takes for half of the nuclides in a sample to decay Example Half-lives polonium seconds lead hours iodine days carbon-145,370 years uranium billion years
D. Half-life How much of a 20-g sample of sodium-24 would remain after decaying for 30 hours? Sodium-24 has a half-life of 15 hours. GIVEN: total time = 30 hours t 1/2 = 15 hours original mass = 20 g WORK : number of half-lives = 2 20 g ÷ 2 = 10 g (1 half- life) 10 g ÷ 2 = 5 g (2 half- lives) 5 g of 24 Na would remain.
CHAPTER 24 Nuclear Energy III. Applications (p ) III. Applications (p )
A. Nuclear Power Fission Reactors Cooling Tower
A. Nuclear Power Fission Reactors
A. Nuclear Power Fusion Reactors (not yet sustainable)
A. Nuclear Power Fusion Reactors (not yet sustainable) Tokamak Fusion Test Reactor Princeton University National Spherical Torus Experiment
A. Nuclear Power 235 U is limited danger of meltdown toxic waste thermal pollution Hydrogen is abundant no danger of meltdown no toxic waste not yet sustainable FISSIONFISSION FUSIONFUSION vs.
B. Others Choose one of the following to investigate: –Irradiated Food (p.676) –Radioactive Dating (p.683) –Nuclear Medicine (p ) Make a mini-poster to display what you have learned.