Phosphorescence
the slow luminescence of substance previously exposed to light
Discovery of Radioactivity
Antoine-Henri Becquerel
Uranic rays
minerals produced rays, like x-rays but not phosphorescence. How Becquerel discovered radioactivity
Marie and Pierre Curie
discovered radium (green glow) and polonium (named for homeland). Renamed it radioactivity since not onyl uranic rays
Radioactivity
release of tiny high-energy particles. Particles ejected from nucleus
Properties of Radioactivity
can ionize matter. High energy rays. Rays Penetrate, can cause chemicals to glow
Alpha rays
charge of +2 and mass of 4. Helium nuclei
Beta rays
charge of -1 and no mass. They are electrons
Gamma Rays
form of light energy, higher than x-rays (0 and 0)
Positron
+1 and no mass. Mass number remains same and atomic number decreases by one when atom looses postiron
Penetrating Power
1) gamma 2) beta 3) alpha
Ionizing energy
1) alpha 2) beta 3) gamma
Parent nuclide
nuclues that is undergoing radio active decay
Daughter nuclide
new nuclei that are made
Beta emission
neutron changes into a proton and electron. Proton remains in nucleu and electron is emitted
Gamma Emission
1) electromagentic radiation- high energy, short wavelength photons 2) low ionizing power 3) high penetrating power
Alpha Emission
1) composed of 2 protons and 2 neutrons 2) high ionizing power 3) low penetrating power
Detecting Radioactivity
1) photographic film to detect presence 2) causes air to become ionized (electroscope and Geiger-Muller) 3) cause certain chemicals to give of flash of light (scintillation counter)
Electroscope
detects radiation by ability to penetrate the flask and ionzie air inside
Geiger-Muller
counts electrons generated when Ar gas atoms are ionzied
Scintillation Counter
counts number of flashes per minute
half-life
length of time it takes for half of a radioactive sample to decay
Decay Series
1) Count number of alpha and beta decays 2) From mass number subtract 4 for each alpha 3)from atomic number subtract 2 for each alpha and 1 for each Beta
Radon
Product of Uranium decay. Can contribute to cancers (lung). Energy efficient buildings with little air exchange with outdoors can build up in radon
Carbon dating
Half-life=5730 years.
Nuclear fission
Lead to Manhattan project b/c thought germany was developing weapons
Fissionable Isotopes
U-235, Pu-239, Pu-240
Nuclear power
Uses fission, 20% u.s. electricity, 70% in france. Heat boils water into steam. Stems turns turbine generating electricity
Fuel Rods
fissionable material stored here
Control Rods
made of neutron asborbing material. Neutrons needed to sustain the chain reaction. Rods placed in material to slow down ejected neutrons called moderators
Concerns Nuclear Power
1) Core melt-down 2) waste disposal 3) transporting waste 4) dealing with plants that are no longer safe
Nuclear Fusion
1) Combing of light nuclei to make heavier one 2) used by weapons and sun (fusion of hydrogen isotopes)
Nuclear weapons
start with small fission to triger the fusion (main bomb)
Biological Effects
1) Acut effects (rapidly dividing cells are sensitive) 2) increased cancer risk (DNA damage causes cell to act wierd) 3) Genetic defects (DNA damage- not observed in humans)
20-100
decreased white blood cell, possible cancer
100-400
radiation sickness; increased cancer risk
500+
death
Sources of Radiation
.3 rem per year from natural causes
Medical use
isotope scanning... organs absorb element... can measure by Geiger, Film, or Scintillation... want short half lifes and low ionizing power
iodine-131
locate tumors in thyroid
Selenium-75
look at pancreas
Gadolinium-153
to determine bone mineralization
Technetium 99m
used for cardiac perfusion.. half life of 6 hrs... very safe... m=metastable
PET Imaging
Positron Emission Tomography... positron annihilates electron to make two gamma rays...radiation in opposite directions
Radiotherapy
used to destroy tumors
Critical Mass
minimus amouint of fissionable isotope needed to sustain the chain reaction
Curies
measures activity of radioactive substance. I cure being 3.7*10^10
Roentgen
measures exposure. 1=2.58*10^-4 per kg of dry air at STP
Roentgen-equivalent man (Rem)
is the effective exposure (ionization) in human tissue. For most roentgen and rem are similar
Factors determining bio effects
1) more energy=larger effect 2)more penetration= more effect 3) more ionization=more effect 4)radioactive half-life 5) biological half-life 6) physical state of radioactive matter