0 RADIATION Energy • in the form of particles • or electromagnetic waves • emitted from the nuclei of unstable atoms 4
0 RADIATION • The term really includes all forms of electromagnetic radiation • Radio Waves, Infrared, Visible Light • Ultraviolet, X-rays, -rays • Commonly used today to describe particle radiation 5
0 NUCLEAR REACTIONS PRODUCE RADIATION • Protons and neutrons determine nuclear reactions • One must understand atomic structure to understand radiation 6
0 NUCLEAR PARTICLES Protons and Neutrons are the two basic nuclear particles. Together they contain practically all the mass of an atom and are determinants of an atom’s nuclear characteristics. 7
0 RADIOACTIVE DECAY • Radioactive decay refers to the spontaneous emission of radiation from the nucleus of an unstable atomic nucleus 8
0 DEFINITION OF RADIOACTIVE DECAY “Radioactive decay is the process of spontaneous emission of radiation in the form of particles or photons from the nuclei of unstable atoms” 9
0 CHARACTERISTICS OF RADIOACTIVE DECAY • It is a natural process in our universe • It is spontaneous – we cannot predict when an atom will undergo decay 10
0 BASIC TYPES OF RADIOACTIVE DECAY Alpha () decay • Occurs when atomic nuclei have too many protons and neutrons (i.e., Are heavy) 11
ALPHA PARTICLE 0 12
0 CHARACTERISTICS OF ALPHA PARTICLES • Consist of 2 protons and 2 neutrons • Mass of an alpha particle is 4 amu • Charge = +2 • The isotope’s Atomic Mass goes down four; • The Atomic Number goes down two • Are highly ionizing • Have low penetrating abilities (only cm in air and mm in water) 13
0 MORE ABOUT ALPHA PARTICLES • Easily shielded; common types of shielding are paper, cardboard, air, clothing; will not penetrate skin • Health hazard when taken internally • Not commonly used in medicine • Common sources = smoke detectors (Am-241) and lantern mantles (thorium nitrate) 14
ALPHA PARTICLE DECAY 0 • Changes both the mass and identity of the nucleus of the parent radionuclide • This means that the decay results in the formation of a new element as the daughter product 15
0 QUESTIONS? ? 16
NEGATIVE BETA (ß-) DECAY 0 Occurs when atoms have too many neutrons (i.e., Are “neutron-rich”) and decay by emitting a negative beta particle (ß-) 17
0 WHAT ARE NEGATIVE BETA PARTICLES? During negative beta decay, neutrons are converted into protons and electrons. The protons remain in the nucleus but the new electrons are emitted as negative beta particles (ß-)or negatrons. You may wish to think of them as “nuclear electrons.” 18
0 CHARACTERISTICS OF NEGATIVE BETA DECAY • Less ionizing than alphas due to decreased mass of negatrons • Changes the identity of the nucleus but not the mass • The Atomic Number is increased by one due to conversion of neutrons into protons 19
CHARACTERISTICS OF NEGATIVE BETA PARTICLES (NEGATRONS) 0 • Negatrons consist of nuclear electrons • The mass is the same as electrons • There is a charge of –1 in negatrons • More penetrating than alpha particles; ~ 12 meters in air • They can penetrate skin– best shielding is wood, plastics, thick cardboard, etc. 20
0 QUESTIONS? ? 24
GAMMA () EMISSION 0 Is a form of pure electromagnetic radiation emitted from nuclei that have excess energy. It is sometimes called gamma photon radiation. 25
GAMMA RAYS 0 Are photons emitted from unstable nuclei to rid themselves of excess energy. Gamma photons are subatomic packets of pure energy. They are higher in energy and more penetrating than thephotons that make up visible light. 26
0 PROPERTIES OF GAMMA () RAYS • Charge is 0 (no charge) • Mass is 0 (no mass) • Low ionization • Penetration abilities can be extremely high; – penetrating power is dependent upon the energy of the emitted photons 28
0 QUESTIONS? ? 29
Positron Negatron Megatron Photon What is a “packet” of light energy that behaves like a particle?
Alpha Decay Beta Decay Gamma Decay Delta Decay Which form of radiation penetrates the least?
Alpha Particle Beta Particle Gamma Particle Delta Particle Which radioactive particle increases the Parent Nucleus’s atomic number?
Alpha Decay Beta Decay Gamma Decay Delta Decay Which form of radiation penetrates the most?
Alpha Particle Beta Particle Gamma Particle Delta Particle Which particle drops the Parent Nucleus’s atomic number by two?
Alpha Particle Beta Particle Gamma Particle Delta Particle Which particle resembles a Helium nucleus?
Alpha Particle Beta Particle Gamma Particle Delta Particle Which particle isn’t a particle but a photon?
Each radioactive element will undergo various forms of radiation until it becomes stable The particular elements that a “Parent Nucleus” changes into are always the same This “path” is a Decay System Decay Systems
Half-life • The amount of time it takes for HALF of an amount of a radioactive material to decay • One symbol for half-life is (lambda)
Fission The splitting of a large, unstable nucleus into two or more stable nuclei Scientists can cause fission by injecting a neutron at high speed These are the uses associated with nuclear fission: Power plants / reactors Bombs “Dirty bombs” Nuclear Processes
Fusion The joining of two or more smaller nuclei into one larger, more stable nucleus Scientists are working on fusion using high pressures, temperatures, and lasers The only place that fusion occurs naturally is stars Nuclear Processes
April 26, 1986 – flawed reactor design was operated by inadequately trained personnel and w/o regard to safety Chernobyl Disaster