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| an atom of an element differing in the number of neutrons in the nucleus but with the same number of protons & electrons |
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| when unstable nuclei emit particles in the form of radiation |
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| an isotope of an element that undergoes radioactive decay |
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naturally occurring radiation from lots of things (from within our cells, from outer space "cosmic rays", radon, rocks & soil)
makes up ~82% of radiation we are exposed to |
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non-natural radiation, comprises ~18% of the radiation we are exposed to
medical x-rays (11%), nuclear medicine, consumer products, occupational radiation, nuclear fuel cycle, other |
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radiation with enough energy to knock electrons from atoms and molecules, converting them to ions
harmful effects can arise from the interaction of radiation and living tissue, as all living things operate on a balance
ex: nuclear radiation, x-rays |
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radiation-caused chemical changes in living cells can be highly disruptive
ionizing radiation can devastate living cells by interfering with their normal chemical processes
molecules can be splintered into reactive fragments called FREE RADICALS
(white blood cells and DNA are particularly vulnerable) |
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(differ from chemical equations because:)
nuclear equations rarely have the same elements on both sides of the arrow (as particles are often emitted, changing the protons and the element)
in nuclear equations we balance NUCLEONS (protons and neutrons) - we focus on balancing the atomic numbers (protons) and nucleon numbers in starting materials and products - MUST SPECIFY ISOTOPE
the number of nucleons in the starting material must equal the total number of nucleons in products - same is true for atomic numbers |
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spontaneous breakdown process of radiation giving off alpha particles - which are identical to helium nuclei (2 neutrons, 2 protons, atomic number 2, nucleon number 4)
ALPHA PARTICLE:
mass of 4u, charge of +2, results in nucleon number decreasing by 4, atomic number decreasing by 2 |
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radioactive breakdown process giving off beta particles - which are identical to electrons
a neutron within the nucleus is converted into a proton which remains and an electron (beta particle) which is ejected
the atomic number increases (1 neutron into 1 proton) but nucleon number remains the same
BETA PARTICLE:
mass of 0, charge of -1, no change in nucleon number, atomic number increases by 1 |
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radioactive breakdown process where gamma rays are emitted
gamma rays have NO MASS and NO CHARGE - neither the nucleon number nor atomic number change, just some energy is released
penetrating power of gamma rays is extremely high as they are so small and energetic - as a high energy photon moving at the speed of light
GAMMA RAY:
no mass, no charge, no change in nucleon number, no change in atomic number |
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radioactive decay process emitting a positron (identical to beta particle but positive in charge) and resulting in a decrease in atomic number of 1, and no change in nucleon number
a proton in the nucleus changes into a neutron and a positron, which is emitted
nucleus has 1 more neutron and 1 less proton, but nucleon number remains the same as total is the same
positrons emitted come in contact with electrons, are obliterated, and release 2 gamma rays
POSITRON:
mass of 0, charge of +1, no change in nucleon number, atomic number decreases by 1 |
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radioactive decay process resulting in a decrease in atomic number of 1, and no change in nucleon number
nucleus absorbs an electron from an inner electron shell (1st or 2nd), energy is released in the form of X-rays as electron moves from shell to nucleus where electron joins with proton to form a neutron
electron is reactant on left side but NOT product on right - product is neutron added
nucleon number remains the same, atomic number decreases by 1
ELECTRON CAPTURE:
no mass, charge of -1, no change in nucleon number, atomic number decreases by 1 |
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time it takes for one half of the original number of atoms of a radioactive isotope to undergo radioactive decay
fraction remaining = 1/2^n |
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| common half-life dating techniques |
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carbon-14: useful for 500 - 50,000 years, organic material, half life 5730 years
hydrogen-3 (titrium): useful for 1-100 years, aged wines, half life 12.26 years
lead-210: useful 1-75 years, skeletal remains, half life 22 years
potassium-40: useful for 10,000-oldest Earth sample years, rocks, Earth's crust, moon's crust, half life 1.25x10^9 years
rhenium-187: useful for 4x10^7 years to oldest samples in universe, meteorites, half life 4.3x10^10 years
uranium-238: useful for 10^7 years-oldest Earth samples, rocks, earth's crust, half life 4.51x10^9 years |
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changing one element into another via altering the nucleus
(ARTIFICIAL TRANSMUTATION): brought on by bombardment of nucleus with alpha particles, neutrons, or other subatomic particles, resulting in radioactive emission |
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| Rutherford's artificial transmutation experiment |
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1919: bombarded a variety of light elements with alpha particles, resulting in production of protons
significance: he obtained protons from the NUCLEUS of an atom other than hydrogen, establishing proton's place in all nuclei - also was the FIRST example of artificial transmutation |
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used in physical, chemical, biological systems to detect decay products and track the movement through a system
isotopes of a given element behave nearly identically in chemical and physical processes, radioactive isotopes are easily detectable through decay products
(detect leaks in underground pipes, determine fictional wear in piston rings, determine the uptake of phosphorous and its distribution in plants) |
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| radioisotopes in agriculture |
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- used for inducing genetic mutations for the safety of a crop
- used for destroying microorganisms that cause food spoilage |
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| radioisotopes in medicine |
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- used for therapeutic reasons
- used for diagnostic reasons (obtaining information about the state of health)
radiation therapy - destroying cancerous cells, lethal to rapidly reproducing cells (cancer cells), concentrated beam to minimize exposure to healthy cells
- thyroid problems, brain problems, heart problems, seeing bone density, etc. |
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- the more massive the particle, the less penetrating power
- the faster a particle moves or the more energetic the radiation, the more penetrating power
in order of most to least penetrating:
gamma rays, beta particles, alpha particles
alpha particles inside the body do lots of damage as they are bigger and don't move far
beta particles inside the body distribute little damage over a larger area - less concentrated damage, easier to recover |
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| the release of nuclear energy by splitting heavy nuclei into smaller nuclei |
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the release of nuclear energy by combining light nuclei to form heavier ones
source of sun's energy |
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e=mc^2
m=mass
e=energy
c=speed of light
mass and energy are just 2 different aspects of the same thing, and little bit of mass can yield enormous energy
a chemical reaction that gives off heat must lose mass in the process, but the change in mass is far too small to measure |
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(protons and neutrons combining to form atomic nuclei, and a small amount of mass is converted to energy) - this is the energy that holds the nucleons together in the nucleus
mass defect - missing mass between calculated mass of all particles in nucleus and actual measurement of nucleus
use einstein's equation to calculate binding energy using mass defect, figure out how much volts required to separate nucleus into constituents - more binding energy required, more stable |
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the process by which nuclear fission can induce nuclear fission of other neighboring atoms and set off a whole group of atoms into fission (by means of bombardment)
Leo Szilard realized this, realized it could be made into a bomb |
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| a secret research project in 1939 on the study of atomic energy, launched by President Roosevelt, in order to construct a bomb using uranium, plutonium, graphite (to slow reactions and increase likelihood that chain would happen) and chain reactions |
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| amount of whatever in a bomb needed to sustain the fission reaction all the way through |
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when a nuclear explosion occurs in the open atmosphere, radioactive materials can rain down on parts of Earth thousands of miles away, days and weeks later
it is very complex, with the most dangerous isotope being strontium-90 (similar to calcium, gets incorporated into bones, source of internal radiation) |
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| difference between power plant and bomb |
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| power plant employs use of slow, controlled release of energy from a nuclear chain reaction (with less enriched uranium), rather than all at once explosion |
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| advantages and disadvantages of nuclear power |
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ADVANTAGES:
reduced CO2 emissions
lower volume of waste than coal/natural gas
lower fuel costs
1/5 the annual occupational health deaths than coal
huge reserves of uranium and thorium - reliable
nuclear power plants operate at industry's highest efficiency percent
DISADVANTAGES:
spent fuel handling and waste storage problems for potential land contamination and broad-scale lethal exposure
potential to be used for deadly weapons
costs a lot to build a power plant |
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reactions that take place in the sun - requiring enormously high temperatures (millions of degrees) to initiate - causing nuclei to fuse and release unimaginable amounts of energy (fusion)
principal reaction of sun:
fusion of 4 hydrogen nuclei to produce 1 helium nucleus and 2 positrons |
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