Ch. 16 Environmental Science. All matter is made of atoms Atoms have Proton Electron Neutrons Nucleus contains protons and neutrons has most of the.

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