What is radiation  A form of energy that can move through empty space.  Transfer of energy by electromagnetic waves

Electromagnetic Spectrum

Types of Radiation  Non-Ionizing - Does not cause atoms to become charged. Microwave, Radio waves, visible light  Ionizing - Can turn atoms of molecules into ions by causing them to lose electrons Most dangerous form of radiation Most dangerous form of radiation Examples: X-Ray and Examples: X-Ray and NUCLEAR RADIATION NUCLEAR RADIATION

What holds the nucleus together?  The strong force acts between protons and neutrons in the nucleus and holds them together  Protons and neutrons have to be close together to be attracted by the strong force (local)  The electric force is a long range force  As the nucleus gets bigger the repulsive electric force increases overcoming the strong force.  The ratio of protons to neutrons indicates whether a nucleus will be stable or unstable.

Stable and Unstable Nuclei  Less massive elements are stable when the ratio of neutrons is about 1 to 1  Heavier elements are stable when the ratio of neutrons to protons is about 3 to 2  So…nuclei with too many or too few neutrons compared to the number of protons are radioactive.  All elements that contain more than 83 protons are radioactive

Challenge Why don’t elements with atomic numbers greater than 92 exist naturally on Earth in significant quantities?  Because they are so unstable that if they are created, they decay almost immediately

Types of Nuclear Radiation  Alpha particles  Beta Particles  Gamma Rays

Alpha Particles  Largest particles  Least penetrating  Loses energy quickly can be stopped by paper  Loses 2 neutrons and 2 protons  Most damaging to tissue if released by radioactive atoms in the body

Polonium  What element does Polonium become after alpha radiation occurs?  Loses 2 neutrons and 2 protons  Lead

Beta Particles  Neutron decays into a proton and emits an electron  Smaller - faster  Stopped by aluminum  Can damage tissue

Bismuth  What element does Bismuth become after beta decay?  Po - Polonium

Gamma Rays  Most penetrating  Travel the speed of light  Usually are released along with alpha and beta particles  They have no mass and no charge  Cause less damage because they pass through tissue

Difference between x-rays and gamma rays  X-Rays originate from the electrons  Gamma rays originate from the nucleus

How do we detect radiation?  Cloud Chamber: Detects alpha beta particles  Geiger Counter: Can detect alpha and beta particles.  Dosimeter: Measures roentgens. How much radiation is taken into the body.

Half Life  The length of time it takes for one half of the sample to decay.  The half-life varies widely from a fraction of a second to billions of year  The nucleus left after the isotope decays is the daughter nucleus

Radioactive Dating

Carbon Dating Used to find the ages of objects once living Decays into nitrogen 14 When an organism dies its carbon-14 atoms decay without being replaced By comparing to the amount of carbon 12 the age of the organism can be determined

Comparison of Chemical and Nuclear Reactions  Chemical  Interactions among outermost electrons  Involves electrons in atomic orbitals  Result in absorption or release of SMALL amounts of energy  Nuclear  Changes in the nuclei of the atoms  Involves protons, neutrons and electrons  Release in a LARGE amount of energy

Nuclear Fission

Nuclear Fusion