ch. 16 environmental science. all matter is made of atoms atoms have proton electron neutrons...
TRANSCRIPT
Ch. 16 Environmental Science
All matter is made of atoms Atoms have
Proton Electron Neutrons
Nucleus contains protons and neutronshas most of the mass
Neutral protons = electrons
Properties determined by protons
Proton number never changes for that element
Atomic number is proton number
Mass number = protons + neutrons
Isotopes – atoms of the same element that have different numbers of neutrons
Uranium 92 protons, 146 neutrons Mass number 238 Isotope U-235, 143 neutrons
Radioactive atomsUnstableDecayEmit particles and
energy from nuclei
Radiation1) alpha particles - 2 protons and 2 neutrons, cannot penetrate skin or paper, but dangerous in lung2) beta particles – high speed electron, can penetrate skin, stopped with aluminum foil3) gamma rays – electromagnetic radiation, can go through body. Can be blocked by several cm of lead or concrete, or 1 m of water
Half-life The amount of time it takes for half the
atoms in a sample of radioactive element to decay
May be a few seconds to billions of years
Nuclear fission A reaction in which the nucleus of a
large atom is split into smaller nuclei
Emits large amounts of energy May be used for electricity
Nuclear Fission U-235 most commonly used Chain reaction releases energy
Nuclear reactor vessel Where the fission of U-234 takes place Used to produce electricity
Heat produced by fission instead of fossil fuels
Breeder reactors Changes U-238 into plutonium-239 Pu-239 used as nuclear fuel Not used in the US because of terrorism
Plutonium used in atomic bombs
Nuclear Reaction-Plutonium video
Nuclear power plants produce radioactive waste
Radiation unhealthy to living cells May cause cancer and genetic
mutations
High level waste – emit large amounts of radiationUranium fuel rodsControl rodsWater used to control the chain reactions
Medium-level and low-level waste are not as radioactive, although more of these are generated
Difficult to dispose of Long half-lives – takes
1000’s of years to decay.
Sealed on containers that will not decay
Stored underground-geologically stable Yucca Mountains,
Nevada Huge environmental
concerns
Meltdown- chain reaction goes out of control and melts the reactor core.
Chernobyl, Ukraine, April 1986-meltdown 116,000 people permanently left At least 15,000 cases of cancer Old plant, lacked many safety features
Utube 20th anniv. Utube